[FIR] Improve diagnostic reporting & don't use error symbol for candidate if possible

Also introduce few new diagnostics:
- NONE_APPLICABLE more many inapplicable candidates
- HIDDEN for visible candidates

compiler/testData/diagnostics/tests/callableReference/genericCallWithReferenceAgainstVararg.fir.kt

@@ -5,9 +5,9 @@ fun foo(vararg ints: Int) {}
 fun test(i: IntArray) {
     myLet(i, ::foo)
     myLet(::foo)
-    <!INAPPLICABLE_CANDIDATE!>myLet<!><Int>(::foo)
+    <!INAPPLICABLE_CANDIDATE!>myLet<!><Int>(<!UNRESOLVED_REFERENCE!>::foo<!>)
     myLet<IntArray>(::foo)
-    <!INAPPLICABLE_CANDIDATE!>myLetExplicit1<!>(::foo)
+    <!INAPPLICABLE_CANDIDATE!>myLetExplicit1<!>(<!UNRESOLVED_REFERENCE!>::foo<!>)
     myLetExplicit2(::foo)
 }