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/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