[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/DeprecatedUnaryOperatorConventions.fir.kt

@@ -16,7 +16,7 @@ operator fun String.unaryPlus(): Int = 0
 fun test() {
     requireInt(+ "")
     requireInt(+ Example())
-    requireString(<!INAPPLICABLE_CANDIDATE!>+<!> ExampleDeprecated())
+    <!INAPPLICABLE_CANDIDATE!>requireString<!>(<!INAPPLICABLE_CANDIDATE!>+<!> ExampleDeprecated())
 }
 
 fun requireInt(n: Int) {}