[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/scopes/kt1738.fir.kt

@@ -6,6 +6,6 @@ class A(private var i: Int, var j: Int) {
 }
 
 fun test(a: A) {
-    a.<!INAPPLICABLE_CANDIDATE, INAPPLICABLE_CANDIDATE!>i<!><!UNRESOLVED_REFERENCE!>++<!>
+    a.<!HIDDEN, HIDDEN!>i<!>++
     a.j++
-}
+}