Add JVM target bytecode version 21

Unfortunately, there are still problems with running JVM backend tests
with JVM target 21 because:

1) The D8 version that we use does not support bytecode version 21, and
   updating to a newer version requires to change JVM target of compiler
   tests to 11. This will be addressed separately when we enable JVM 21
   in tests-different-jdk.
2) Some tests are failing because of KT-60659 and KT-60770:
   - builtinStubMethods/bridgesForStubs/emptyStringListAdd.kt
   - jdk/stream.kt
   - regressions/kt528.kt

 #KT-60662 Fixed

compiler/config.jvm/src/org/jetbrains/kotlin/config/JvmTarget.kt

@@ -37,6 +37,7 @@ enum class JvmTarget(
     JVM_18("18", Opcodes.V16 + 2),
     JVM_19("19", Opcodes.V16 + 3),
     JVM_20("20", Opcodes.V16 + 4),
+    JVM_21("21", Opcodes.V16 + 5),
     ;
 
     override fun toString() = description
@@ -46,10 +47,10 @@ enum class JvmTarget(
         val DEFAULT = JVM_1_8
 
         @JvmStatic
-        fun fromString(string: String) = values().find { it.description == string }
+        fun fromString(string: String) = entries.find { it.description == string }
 
         fun getDescription(majorVersion: Int): String {
-            val platformDescription = values().find { it.majorVersion == majorVersion }?.description ?: when (majorVersion) {
+            val platformDescription = entries.find { it.majorVersion == majorVersion }?.description ?: when (majorVersion) {
                 Opcodes.V1_7 -> "1.7"
                 else -> null
             }
@@ -59,13 +60,13 @@ enum class JvmTarget(
         }
 
         fun supportedValues(): List<JvmTarget> =
-            values().asList() - JVM_1_6
+            entries - JVM_1_6
 
         const val SUPPORTED_VERSIONS_DESCRIPTION =
-            "1.8, 9, 10, ..., 20"
+            "1.8, 9, 10, ..., 21"
 
         init {
-            check(SUPPORTED_VERSIONS_DESCRIPTION == "1.8, 9, 10, ..., ${values().last().description}") {
+            check(SUPPORTED_VERSIONS_DESCRIPTION == "1.8, 9, 10, ..., ${entries.last().description}") {
                 "Please update the value of the constant JvmTarget.SUPPORTED_VERSIONS_DESCRIPTION."
             }
         }

compiler/testData/cli/jvm/extraHelp.out

@@ -42,7 +42,7 @@ where advanced options include:
   -Xjava-source-roots=<path> Paths to directories with Java source files
   -Xjavac-arguments=<option[,]> Java compiler arguments
   -Xjdk-release=<version>    Compile against the specified JDK API version, similarly to javac's `-release`. Requires JDK 9 or newer.
-                             Supported versions depend on the used JDK; for JDK 17+ supported versions are 1.8, 9, 10, ..., 20.
+                             Supported versions depend on the used JDK; for JDK 17+ supported versions are 1.8, 9, 10, ..., 21.
                              Also sets `-jvm-target` value equal to the selected JDK version
   -Xjspecify-annotations=ignore|strict|warn
                              Specify behavior for jspecify annotations.

compiler/testData/cli/jvm/help.out

@@ -6,7 +6,7 @@ where possible options include:
   -include-runtime           Include Kotlin runtime into the resulting JAR
   -java-parameters           Generate metadata for Java 1.8 reflection on method parameters
   -jdk-home <path>           Include a custom JDK from the specified location into the classpath instead of the default JAVA_HOME
-  -jvm-target <version>      Target version of the generated JVM bytecode (1.8, 9, 10, ..., 20), default is 1.8
+  -jvm-target <version>      Target version of the generated JVM bytecode (1.8, 9, 10, ..., 21), default is 1.8
   -module-name <name>        Name of the generated .kotlin_module file
   -no-jdk                    Don't automatically include the Java runtime into the classpath
   -no-reflect                Don't automatically include Kotlin reflection into the classpath

compiler/testData/cli/jvm/wrongJvmTargetVersion.out

@@ -1,3 +1,3 @@
 error: unknown JVM target version: 1.5
-Supported versions: 1.6, 1.8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20
+Supported versions: 1.6, 1.8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21
 COMPILATION_ERROR

compiler/testData/codegen/box/reflection/classes/nestedClasses.kt

@@ -26,7 +26,7 @@ fun box(): String {
     // Java interface with nested classes
     assertEquals(listOf("Entry"), nestedNames(java.util.Map::class))
     // Java class with nested classes
-    assertEquals(listOf("SimpleEntry", "SimpleImmutableEntry"), nestedNames(java.util.AbstractMap::class))
+    assertEquals(listOf("SimpleEntry", "SimpleImmutableEntry"), nestedNames(java.util.AbstractMap::class) - "ViewCollection")
 
     // Built-ins
     assertEquals(emptyList<String>(), nestedNames(Array<Any>::class))

libraries/tools/kotlin-gradle-compiler-types/src/generated/kotlin/org/jetbrains/kotlin/gradle/dsl/JvmTarget.kt

@@ -19,6 +19,7 @@ enum class JvmTarget(val target: String) {
     JVM_18("18"),
     JVM_19("19"),
     JVM_20("20"),
+    JVM_21("21"),
     ;
 
     companion object {

libraries/tools/kotlin-gradle-plugin-api/api/kotlin-gradle-plugin-api.api

@@ -92,6 +92,7 @@ public final class org/jetbrains/kotlin/gradle/dsl/JvmTarget : java/lang/Enum {
 	public static final field JVM_19 Lorg/jetbrains/kotlin/gradle/dsl/JvmTarget;
 	public static final field JVM_1_8 Lorg/jetbrains/kotlin/gradle/dsl/JvmTarget;
 	public static final field JVM_20 Lorg/jetbrains/kotlin/gradle/dsl/JvmTarget;
+	public static final field JVM_21 Lorg/jetbrains/kotlin/gradle/dsl/JvmTarget;
 	public static final field JVM_9 Lorg/jetbrains/kotlin/gradle/dsl/JvmTarget;
 	public final fun getTarget ()Ljava/lang/String;
 	public static fun valueOf (Ljava/lang/String;)Lorg/jetbrains/kotlin/gradle/dsl/JvmTarget;

libraries/tools/kotlin-gradle-plugin-api/src/common/kotlin/org/jetbrains/kotlin/gradle/dsl/KotlinJvmCompilerOptions.kt

@@ -15,8 +15,8 @@ interface KotlinJvmCompilerOptions : org.jetbrains.kotlin.gradle.dsl.KotlinCommo
     val javaParameters: org.gradle.api.provider.Property<kotlin.Boolean>
 
     /**
-     * Target version of the generated JVM bytecode (1.8, 9, 10, ..., 20), default is 1.8
-     * Possible values: "1.8", "9", "10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "20"
+     * Target version of the generated JVM bytecode (1.8, 9, 10, ..., 21), default is 1.8
+     * Possible values: "1.8", "9", "10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "20", "21"
      * Default value: JvmTarget.DEFAULT
      */
     @get:org.gradle.api.tasks.Input

libraries/tools/kotlin-gradle-plugin-api/src/common/kotlin/org/jetbrains/kotlin/gradle/dsl/KotlinJvmOptions.kt

@@ -21,8 +21,8 @@ interface KotlinJvmOptions : org.jetbrains.kotlin.gradle.dsl.KotlinCommonOptions
     private val org.jetbrains.kotlin.gradle.dsl.JvmTarget.jvmTargetKotlinOption get() = this.target
 
     /**
-     * Target version of the generated JVM bytecode (1.8, 9, 10, ..., 20), default is 1.8
-     * Possible values: "1.8", "9", "10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "20"
+     * Target version of the generated JVM bytecode (1.8, 9, 10, ..., 21), default is 1.8
+     * Possible values: "1.8", "9", "10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "20", "21"
      * Default value: JvmTarget.DEFAULT
      */
     var jvmTarget: kotlin.String