[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/smartCasts/intersectionScope/unstableSmartCast.fir.kt

@@ -33,6 +33,6 @@ fun test() {
         x.baz(1).checkType { _<Unit>() }
         x.<!INAPPLICABLE_CANDIDATE!>baz<!>(1, 2)
 
-        x.<!UNRESOLVED_REFERENCE!>foobar<!>().<!INAPPLICABLE_CANDIDATE!>checkType<!> { <!UNRESOLVED_REFERENCE!>_<!><String>() }
+        x.<!UNRESOLVED_REFERENCE!>foobar<!>().<!INAPPLICABLE_CANDIDATE!>checkType<!> { <!INAPPLICABLE_CANDIDATE!>_<!><String>() }
     }
 }