KT-64385 Enable K2 KAPT by default

Also adds support for front-end compiler plugins in Kapt

plugins/kapt3/kapt3-cli/testData/integration/fallback/build.txt

@@ -1,69 +0,0 @@
-# mkdir
-output/stubs
-output/classes
-output/javaClasses
-output/sources
-output/stubsAlt
-output/classesAlt
-output/javaClassesAlt
-output/sourcesAlt
-
-# kotlinc
--language-version 2.0
--cp %KOTLIN_STDLIB%
--d output/ap.jar
-ap/Processor.kt
-
-# copy
-ap/META-INF/services/javax.annotation.processing.Processor
-output/ap/META-INF/services/javax.annotation.processing.Processor
-
-# kapt
--Xuse-k2
--Kapt-stubs=output/stubs
--Kapt-classes=output/classes
--Kapt-sources=output/sources
--Kapt-classpath=output/ap
--d output/classes
--cp output/ap.jar:%KOTLIN_STDLIB%
-Test.kt
-
-# javac
--cp output/ap.jar
--d output/javaClasses
--proc:none
-output/sources/generated/Function.java
-output/sources/generated/Property.java
-output/sources/generated/Test.java
-
-# kapt
--language-version 2.0
--Kapt-stubs=output/stubsAlt
--Kapt-classes=output/classesAlt
--Kapt-sources=output/sourcesAlt
--Kapt-classpath=output/ap
--d output/classesAlt
--cp output/ap.jar:%KOTLIN_STDLIB%
-Test.kt
-
-# output
-warning: kapt currently doesn't support language version 2.0+. Falling back to 1.9.
-
-# java
--cp output/classes:output/javaClasses:output/ap.jar:%KOTLIN_STDLIB%
-test.TestKt
-
-# javac
--cp output/ap.jar
--d output/javaClassesAlt
--proc:none
-output/sourcesAlt/generated/Function.java
-output/sourcesAlt/generated/Property.java
-output/sourcesAlt/generated/Test.java
-
-# java
--cp output/classes:output/javaClassesAlt:output/ap.jar:%KOTLIN_STDLIB%
-test.TestKt
-
-# after
-Generated class: generated.Test