FIR: add UnsafeCall resolution diagnostics

Previously unsafe call is reported as part of InapplicableWrongReceiver.
This makes it difficult for the downstream checkers to report different
diagnostics.

compiler/testData/diagnostics/testsWithStdLib/coroutines/restrictSuspension/outerYield_1_3.fir.kt

@@ -87,7 +87,7 @@ fun test() {
                 this@with.<!UNRESOLVED_REFERENCE!>yield<!>("")
 
                 yield2("")
-                this@with<!UNSAFE_CALL!>.<!>yield2("")
+                this@with.<!INAPPLICABLE_CANDIDATE!>yield2<!>("")
             }
         }
     }