[FIR] When call candidates resolve to errors, select the least bad ones

This fixes a scenario when INVISIBLE_REFERENCE is suppressed, but we
resolved to the wrong overload because when none of the candidates were
applicable, more or less the first one was chosen.

Because we call `fullyProcessCandidate` on the candidates, their
applicability can change which can lead to a situation where the
applicability of a ConeAmbiguityError is different to all its
candidates. The changes in coneDiagnosticToFirDiagnostic.kt account for
that, otherwise code like candidates.first { it.applicability ==
CandidateApplicability.UNSAFE_CALL } can throw NoSuchElementException.

#KT-57776 Fixed

compiler/testData/diagnostics/tests/overload/onlyPrivateOverloadsDiagnostic.fir.kt

@@ -6,7 +6,7 @@ class A {
 }
 
 fun test(a: A) {
-    a.<!NONE_APPLICABLE!>foo<!>(3)
+    a.<!INVISIBLE_REFERENCE!>foo<!>(3)
     a.<!NONE_APPLICABLE!>foo<!>()
 }