KT-64385 Enable K2 KAPT by default

Also adds support for front-end compiler plugins in Kapt

plugins/kapt3/kapt3-cli/src/KaptCli.kt

@@ -107,7 +107,6 @@ private fun transformKaptToolArgs(args: List<String>, messageCollector: MessageC
             }
             KaptCliOption.APT_MODE_OPTION -> aptModePassed = true
             KaptCliOption.VERBOSE_MODE_OPTION -> kaptVerboseModePassed = true
-            KaptCliOption.USE_K2 -> transformed.add("-Xuse-kapt4")
             else -> {}
         }
 
@@ -115,7 +114,7 @@ private fun transformKaptToolArgs(args: List<String>, messageCollector: MessageC
     }
 
     if (!aptModePassed) {
-        val isK2 = "-Xuse-kapt4" in transformed && ("-Xuse-k2" in transformed ||
+        val isK2 = ("-Xuse-k2" in transformed ||
                 transformed.any { it.startsWith("-language-version=2") } ||
                 transformed.lastIndexOf("-language-version").takeIf { it >= 0 }
                     ?.let { transformed.getOrNull(it + 1)?.startsWith('2') } == true)

plugins/kapt3/kapt3-cli/src/KaptCliOption.kt

@@ -214,13 +214,6 @@ enum class KaptCliOption(
         "Keep KDoc comments in stubs"
     ),
 
-    USE_K2(
-        "useK2",
-        "true | false",
-        "Use K2",
-        cliToolOption = CliToolOption("-Kapt-use-k2", FLAG)
-    ),
-
     DETECT_MEMORY_LEAKS_OPTION("detectMemoryLeaks", "true | false", "Detect memory leaks in annotation processors"),
     INCLUDE_COMPILE_CLASSPATH(
         "includeCompileClasspath",