[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/InaccessiblePrivateClass.fir.kt

@@ -15,4 +15,4 @@ package p1
 import p2.*
 
 val <!EXPOSED_PROPERTY_TYPE!>x<!>: X = X()
-val <!EXPOSED_PROPERTY_TYPE!>y<!>: Y = <!INAPPLICABLE_CANDIDATE!>Y<!>()
+val <!EXPOSED_PROPERTY_TYPE!>y<!>: Y = <!HIDDEN!>Y<!>()