[FIR JS] Support JS_NAME_CLASH and JS_FAKE_NAME_CLASH diagnostics

^KT-59425 Fixed
^KT-59370 Fixed

compiler/testData/diagnostics/testsWithJsStdLib/name/packageAndMethod.kt

@@ -1,3 +1,6 @@
+// FIR_DIFFERENCE
+// This case can't be checked using FIR. It is checked later on klib serialization.
+
 // FILE: foo.kt
 
 package foo