[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/kt1805.fir.kt

@@ -7,14 +7,14 @@ open class Some {
 
 class SomeSubclass : Some() {
     fun test() {
-        this.<!INAPPLICABLE_CANDIDATE!>privateField<!> // 1. Unresolved reference
+        this.<!HIDDEN!>privateField<!> // 1. Unresolved reference
     }
 }
 
 fun test() {
     val s2 = Some()
-    s2.<!INAPPLICABLE_CANDIDATE!>privateField<!> // 2. Can't access to 'privateField' in Some
+    s2.<!HIDDEN!>privateField<!> // 2. Can't access to 'privateField' in Some
 
     val s1 = SomeSubclass()
-    s1.<!INAPPLICABLE_CANDIDATE!>privateField<!> // 3. Unresolved reference
-}
+    s1.<!HIDDEN!>privateField<!> // 3. Unresolved reference
+}