Support for new double colon expressions in type checker

Despite the fact that the LHS of a double colon expression is now KtExpression
instead of KtUserType, we must still consider it a type for callable references
to work. Extract and reuse relevant parts of QualifiedExpressionResolver and
TypeResolver to support this behavior

compiler/testData/diagnostics/tests/callableReference/whitespacesInExpression.txt

@@ -0,0 +1,11 @@
+package
+
+public fun test(): kotlin.Unit
+public fun Foo?.bar(): kotlin.Unit
+
+public final class Foo {
+    public constructor Foo()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}