[KAPT4] KT-61761 Prevent Kapt from reporting unsupported plugin in K2/PSI

Also:
- remove the redundant KaptOptions.USE_K2
- prevent registration of Kapt4AnalysisHandlerExtension in K1

plugins/kapt3/kapt3-base/src/org/jetbrains/kotlin/kapt3/base/KaptOptions.kt

@@ -130,7 +130,6 @@ enum class KaptFlag(val description: String, val defaultValue: Boolean = false)
     STRIP_METADATA("Strip @Metadata annotations from stubs"),
     KEEP_KDOC_COMMENTS_IN_STUBS("Keep KDoc comments in stubs", defaultValue = true),
     USE_JVM_IR("Use JVM IR backend", defaultValue = true),
-    USE_K2("Use K2"),
     ;
 }