Cleanup

- do not use annotation resolve in CodegenFileClassProvider
- test using private methods across different parts of multifile class

compiler/testData/codegen/boxWithJava/fileClasses/multifileClassWith2Files/foo.kt

@@ -1,3 +1,2 @@
-@file:JvmName("Util")
-@file:JvmMultifileClass
+@file:[JvmName("Util") JvmMultifileClass]
 public fun foo(): String = "O"

compiler/testData/codegen/boxWithJava/fileClasses/multifileClassWithCrossPrivate/bar.kt

@@ -2,4 +2,4 @@
 @file:JvmMultifileClass
 public fun bar(): String = barx()
 
-internal fun foox(): String = "O"
+private fun foox(): String = "O"

compiler/testData/codegen/boxWithJava/fileClasses/multifileClassWithCrossPrivate/foo.kt

@@ -2,4 +2,4 @@
 @file:JvmMultifileClass
 public fun foo(): String = foox()
 
-internal fun barx(): String = "K"
+private fun barx(): String = "K"