FIR checker: report UNSAFE_CALL for overloaded function calls

Previously if an unsafe call is to an overloaded function, FIR checkers
report NONE_APPLICABLE. This change instead report them as UNSAFE_CALL
or its variants.

compiler/testData/diagnostics/tests/BinaryCallsOnNullableValues.fir.kt

@@ -6,9 +6,9 @@ class A() {
 fun f(): Unit {
     var x: Int? = 1
     x = null
-    x <!NONE_APPLICABLE!>+<!> 1
-    x <!NONE_APPLICABLE!>plus<!> 1
-    x <!NONE_APPLICABLE!><<!> 1
+    x <!UNSAFE_OPERATOR_CALL!>+<!> 1
+    x <!UNSAFE_CALL!>plus<!> 1
+    x <!UNSAFE_OPERATOR_CALL!><<!> 1
     x <!UNRESOLVED_REFERENCE!>+=<!> 1
 
     x == 1
@@ -22,7 +22,7 @@ fun f(): Unit {
     x === 1
     x !== 1
 
-    x<!NONE_APPLICABLE!>..<!>2
+    x<!UNSAFE_OPERATOR_CALL!>..<!>2
     <!ARGUMENT_TYPE_MISMATCH!>x<!> in 1..2
 
     val y : Boolean? = true