KT-22274 report warning on labels that can't be referenced

Labels are meaningful only if they can be referenced by 'break',
'continue', or 'return' expressions.

compiler/testData/diagnostics/tests/deparenthesize/ParenthesizedVariable.kt

@@ -1,3 +1,3 @@
 fun test() {
-    (d@ <!DECLARATION_IN_ILLEGAL_CONTEXT!>val <!UNUSED_VARIABLE!>bar<!> = 2<!>)
+    (<!REDUNDANT_LABEL_WARNING!>d@<!> <!DECLARATION_IN_ILLEGAL_CONTEXT!>val <!UNUSED_VARIABLE!>bar<!> = 2<!>)
 }

compiler/testData/diagnostics/tests/deparenthesize/checkDeparenthesizedType.kt

@@ -5,19 +5,19 @@ package m
 
 fun test(i: Int?) {
     if (i != null) {
-        foo(l1@ <!DEBUG_INFO_SMARTCAST!>i<!>)
+        foo(<!OI;REDUNDANT_LABEL_WARNING!>l1@<!> <!DEBUG_INFO_SMARTCAST!>i<!>)
         foo((<!DEBUG_INFO_SMARTCAST!>i<!>))
-        foo(l2@ (<!DEBUG_INFO_SMARTCAST!>i<!>))
-        foo((l3@ <!DEBUG_INFO_SMARTCAST!>i<!>))
+        foo(<!OI;REDUNDANT_LABEL_WARNING!>l2@<!> (<!DEBUG_INFO_SMARTCAST!>i<!>))
+        foo((<!OI;REDUNDANT_LABEL_WARNING!>l3@<!> <!DEBUG_INFO_SMARTCAST!>i<!>))
     }
 
-    val a: Int = l4@ <!TYPE_MISMATCH!>""<!>
+    val a: Int = <!OI;REDUNDANT_LABEL_WARNING!>l4@<!> <!TYPE_MISMATCH!>""<!>
     val b: Int = (<!TYPE_MISMATCH!>""<!>)
     val c: Int = checkSubtype<Int>(<!TYPE_MISMATCH!>""<!>)
     val d: Int = <!NI;TYPE_MISMATCH, NI;TYPE_MISMATCH, TYPE_MISMATCH!>checkSubtype<Long>(<!TYPE_MISMATCH!>""<!>)<!>
 
 
-    foo(l4@ <!TYPE_MISMATCH!>""<!>)
+    foo(<!OI;REDUNDANT_LABEL_WARNING!>l4@<!> <!TYPE_MISMATCH!>""<!>)
     foo((<!TYPE_MISMATCH!>""<!>))
     foo(checkSubtype<Int>(<!NI;TYPE_MISMATCH, NI;TYPE_MISMATCH, TYPE_MISMATCH!>""<!>))
     foo(<!NI;TYPE_MISMATCH, TYPE_MISMATCH!>checkSubtype<Long>(<!NI;TYPE_MISMATCH, NI;TYPE_MISMATCH, TYPE_MISMATCH!>""<!>)<!>)

compiler/testData/diagnostics/tests/deparenthesize/labeledSafeCall.kt

@@ -1,3 +1,3 @@
 fun f(s : String?) : Boolean {
-    return foo@(s?.equals("a"))!!
+    return <!REDUNDANT_LABEL_WARNING!>foo@<!>(s?.equals("a"))!!
 }