[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/resolve/specialConstructions/elvisAsCall.fir.kt

@@ -23,15 +23,15 @@ fun testDataFlowInfo1(a: Int?, b: Int?) {
     val c: Int = a ?: b!!
     doInt(c)
     // b is nullable if a != null
-    b <!INAPPLICABLE_CANDIDATE!>+<!> 1
+    b <!NONE_APPLICABLE!>+<!> 1
 }
 
 fun testDataFlowInfo2(a: Int?, b: Int?) {
     doInt(a ?: b!!)
     // b is nullable if a != null
-    b <!INAPPLICABLE_CANDIDATE!>+<!> 1
+    b <!NONE_APPLICABLE!>+<!> 1
 }
 
 fun testTypeMismatch(a: String?, b: Any) {
     <!INAPPLICABLE_CANDIDATE!>doInt<!>(a ?: b)
-}
+}