Kapt: Move line metadata to .kaptMetadata external files (KT-22386)

Placing location table inside .java file triggers annotation processor to run on each line table modification (even when the stub declarations themselves are the same). So we move it to the separate file.

plugins/kapt3/kapt3-compiler/testData/kotlinRunner/NestedClasses.it.txt

@@ -1,6 +1,10 @@
-/**
- * @KaptMetadata
- */
+package error;
+
+public final class NonExistentClass {
+}
+
+////////////////////
+
 package test;
 
 import java.lang.System;
@@ -12,9 +16,6 @@ public abstract @interface MyAnnotation {
 
 ////////////////////
 
-/**
- * @KaptMetadata
- */
 package test;
 
 import java.lang.System;
@@ -63,10 +64,3 @@ public final class Simple {
         }
     }
 }
-
-////////////////////
-
-package error;
-
-public final class NonExistentClass {
-}