[java decompiler] improves anonymous classes verification

- puts the check under an option
- uses 'EnclosingMethod' attribute to skip unrelated methods

plugins/java-decompiler/plugin/src/org/jetbrains/java/decompiler/IdeaDecompiler.kt

@@ -62,6 +62,7 @@ class IdeaDecompiler : ClassFileDecompilers.Light() {
         IFernflowerPreferences.MAX_PROCESSING_METHOD to 60,
         IFernflowerPreferences.INDENT_STRING to indent,
         IFernflowerPreferences.IGNORE_INVALID_BYTECODE to "1",
+        IFernflowerPreferences.VERIFY_ANONYMOUS_CLASSES to "1",
         IFernflowerPreferences.UNIT_TEST_MODE to if (ApplicationManager.getApplication().isUnitTestMode) "1" else "0")
     }
   }