Introduce FIR_IDENTICAL for FIR vs old frontend tests #KT-36879 Fixed

compiler/testData/diagnostics/tests/operatorRem/operatorRem.fir.kt

@@ -1,15 +0,0 @@
-// !DIAGNOSTICS: -UNUSED_PARAMETER, -UNUSED_VARIABLE
-
-class Foo {
-    operator fun rem(x: Int): Foo = Foo()
-}
-
-class Bar {
-    operator fun remAssign(x: Int) {}
-}
-
-fun baz() {
-    val f = Foo() % 1
-    val b = Bar()
-    b %= 1
-}

compiler/testData/diagnostics/tests/operatorRem/operatorRem.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // !DIAGNOSTICS: -UNUSED_PARAMETER, -UNUSED_VARIABLE
 
 class Foo {