FIR checker: check if callable reference targets are allowed members

compiler/testData/diagnostics/tests/callableReference/unsupported/parameterWithSubstitution.fir.kt

@@ -9,6 +9,6 @@ class Foo {
 fun main(x: Int) {
     val f = Foo()
     val a: Int
-    <!VARIABLE_EXPECTED!>get()<!> = f.getValue(null, ::x) // no exception after fix
+    <!VARIABLE_EXPECTED!>get()<!> = f.getValue(null, <!UNSUPPORTED!>::x<!>) // no exception after fix
     <!UNRESOLVED_REFERENCE!>print<!>(<!UNINITIALIZED_VARIABLE!>a<!>)
-}
+}