[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/imports/ImportPrivateMember.fir.kt

@@ -29,9 +29,9 @@ private object TopLevelObject {
 }
 
 fun testAccess() {
-    <!INAPPLICABLE_CANDIDATE!>NestedClass<!>()
+    <!HIDDEN!>NestedClass<!>()
     E1
     InNested()
     NestedEntry
     inObject()
-}
+}