Fix GDScript base and outer classes, signals and functions lookup order

- Add outer class lookup test
- Add signal lookup test

Co-authored-by: Dmitrii Maganov <vonagam@gmail.com>

modules/gdscript/tests/scripts/analyzer/features/lookup_signal.gd

@@ -0,0 +1,41 @@
+signal hello
+
+func get_signal() -> Signal:
+    return hello
+
+class A:
+    signal hello
+
+    func get_signal() -> Signal:
+        return hello
+
+    class B:
+        signal hello
+
+        func get_signal() -> Signal:
+            return hello
+
+class C extends A.B:
+    func get_signal() -> Signal:
+        return hello
+
+func test():
+    var a: = A.new()
+    var b: = A.B.new()
+    var c: = C.new()
+
+    var hello_a_result: = hello == a.get_signal()
+    var hello_b_result: = hello == b.get_signal()
+    var hello_c_result: = hello == c.get_signal()
+    var a_b_result: = a.get_signal() == b.get_signal()
+    var a_c_result: = a.get_signal() == c.get_signal()
+    var b_c_result: = b.get_signal() == c.get_signal()
+    var c_c_result: = c.get_signal() == c.get_signal()
+
+    print("hello == A.hello? %s" % hello_a_result)
+    print("hello == A.B.hello? %s" % hello_b_result)
+    print("hello == C.hello? %s" % hello_c_result)
+    print("A.hello == A.B.hello? %s" % a_b_result)
+    print("A.hello == C.hello? %s" % a_c_result)
+    print("A.B.hello == C.hello? %s" % b_c_result)
+    print("C.hello == C.hello? %s" % c_c_result)