FIR checker: report REDUNDANT_LABEL_WARNING

Since many labels are not present in the FIR tree, this checker is
implemented as a syntax checker. Comparing with FE1.0, this change
reports some REDUNDANT_LABEL_WARNING that FE1.0 has missed, especially
LHS of assignments.

compiler/testData/diagnostics/tests/inference/expectedTypeFromCastParenthesized.fir.kt

@@ -1,22 +0,0 @@
-// !LANGUAGE: +ExpectedTypeFromCast
-
-@Target(AnnotationTarget.EXPRESSION)
-@Retention(AnnotationRetention.SOURCE)
-annotation class bar
-
-fun <T> foo(): T = TODO()
-
-fun <V> id(value: V) = value
-
-val par1 = (foo()) as String
-val par2 = ((foo())) as String
-
-val par3 = (dd@ (foo())) as String
-
-val par4 = ( @bar() (foo())) as String
-
-object X {
-    fun <T> foo(): T = TODO()
-}
-
-val par5 = ( @bar() X.foo()) as String

compiler/testData/diagnostics/tests/inference/expectedTypeFromCastParenthesized.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // !LANGUAGE: +ExpectedTypeFromCast
 
 @Target(AnnotationTarget.EXPRESSION)