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/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