KT-64385 Enable K2 KAPT by default

Also adds support for front-end compiler plugins in Kapt

plugins/kapt3/kapt3-cli/testData/integration/fallback/Test.kt

@@ -1,19 +0,0 @@
-package test
-
-import apt.Anno
-import generated.Test as TestGenerated
-
-@Anno
-class Test {
-    @field:Anno
-    val property: String = ""
-
-    @Anno
-    fun function() {
-
-    }
-}
-
-fun main() {
-    println("Generated class: " + TestGenerated::class.java.name)
-}