[FIR] Consider @PlatformDependent annotation everywhere (including JS and Native)

^KT-57858 Fixed

Remove FirEmptyOverridesBackwardCompatibilityHelper since it's not used anymore

Remove overridesMemberWithPlatformDependent.kt test file since it becomes redundant

compiler/testData/diagnostics/testsWithJsStdLib/overridesMemberWithPlatformDependent.kt

@@ -1,14 +0,0 @@
-// FIR_IDENTICAL
-// ISSUE: KT-57858
-@file:Suppress("INVISIBLE_MEMBER", "INVISIBLE_REFERENCE")
-
-import kotlin.internal.PlatformDependent
-
-interface I {
-    @PlatformDependent
-    fun f() {}
-}
-
-class C : I {
-    fun <!VIRTUAL_MEMBER_HIDDEN!>f<!>() {}
-}