Resolve callable reference expressions

#KT-1183 In Progress

compiler/testData/diagnostics/tests/callableReference/extensionFromTopLevel.kt

@@ -0,0 +1,15 @@
+class A
+
+fun A.foo() {}
+fun A.bar(<!UNUSED_PARAMETER!>x<!>: Int) {}
+fun A.baz() = "OK"
+
+fun main() {
+    val x = A::foo
+    val y = A::bar
+    val z = A::baz
+
+    x : KExtensionFunction0<A, Unit>
+    y : KExtensionFunction1<A, Int, Unit>
+    z : KExtensionFunction0<A, String>
+}