Support overload ambiguity resolution for callable references by expected type.

Resolve callable references taking into account expected callable types.

This affects call resolution procedure (resolve 'foo' in for 'foo(::bar)') similar to the approach used for function literals:

* During "shape arguments" phase of call resolution, callable references are resolved in independent context without expected type. If the callable reference is ambiguous, its shape type is a function placeholder type without parameter types and return type information. Otherwise, it is a reflection type for the resolved function or property. Upper-level call is resolved without taking into account ambiguous callable references.

* During "complete call" phase of call resolution, resolve callable reference arguments to actual descriptors (if possible), and update constraint system for the given call accordingly.

 #KT-6982 Fixed
 #KT-5780 Fixed

compiler/testData/diagnostics/tests/callableReference/resolve/constructor.kt

@@ -0,0 +1,12 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+class Klass {
+    constructor(a: Int) {}
+    constructor(a: String) {}
+}
+
+fun user(f: (Int) -> Klass) {}
+
+fun fn() {
+    user(::Klass)
+}