[JS FIR] Rework JS_NAME_CLASH diagnostic for constructors

- Fix a false positive JS_NAME_CLASH report on constructors
   from different classes but with the same JsName.
 - Allow the same JsName for class constructors and other top-level
   declarations. This behavior differs from K1, but it is correct
   since there is no real name clash in the generated JS code.

^KT-64867 Fixed

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

@@ -1,4 +1,7 @@
-// FIR_IDENTICAL
+// FIR_DIFFERENCE
+// K1 performs a check for legacy JS BE; however, this is not relevant for IR BE because in the generated JS code,
+// there is no name clash between the constructor with JsName and the other top-level declarations with the same JsName.
+// Keep K1 as it is, but for K2, implement a more relevant check without the clash.
 package foo
 
 class A(val x: String) {