[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/overload/onlyPrivateOverloadsDiagnostic.fir.kt

@@ -6,7 +6,7 @@ class A {
 }
 
 fun test(a: A) {
-    a.<!INAPPLICABLE_CANDIDATE!>foo<!>(3)
-    a.<!INAPPLICABLE_CANDIDATE!>foo<!>()
+    a.<!NONE_APPLICABLE!>foo<!>(3)
+    a.<!NONE_APPLICABLE!>foo<!>()
 }