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/fir/analysis-tests/testData/resolveWithStdlib/contracts/fromLibrary/notIsNullOrEmpty.fir.txt

@@ -10,7 +10,7 @@ FILE: notIsNullOrEmpty.kt
     public final fun test_2(s: R|kotlin/String?|): R|kotlin/Unit| {
         when () {
             R|<local>/s|.R|kotlin/text/isNullOrEmpty|() ->  {
-                R|<local>/s|.<Inapplicable(INAPPLICABLE_WRONG_RECEIVER): kotlin/String.length>#
+                R|<local>/s|.<Inapplicable(UNSAFE_CALL): kotlin/String.length>#
             }
             else ->  {
                 R|<local>/s|.R|kotlin/String.length|