Fix analyzer pushing SHADOWED_VARIABLE warning for members shadowed in subclasses

This fixes a bug in the analyzer where it did not push the SHADOWED_VARIABLE_BASE_CLASS
warning for members shadowed by variable in subclass. It does this by comparing the class
which contains the shadowed member with the class containing the variable, and pushing
SHADOWED_VARIABLE only if the classes are the same. Additionally, SHADOWED_VARIABLE_BASE_CLASS
can take an extra symbol which helps to specify the line for non native base class.

modules/gdscript/tests/scripts/analyzer/warnings/shadowning.gd

@@ -1,4 +1,5 @@
 class_name ShadowedClass
+extends ShadowingBase
 
 var member: int = 0
 
@@ -7,6 +8,7 @@ var print_debug := 'print_debug'
 var print := 'print'
 
 @warning_ignore("unused_variable")
+@warning_ignore("unused_local_constant")
 func test():
 	var Array := 'Array'
 	var Node := 'Node'
@@ -15,5 +17,8 @@ func test():
 	var member := 'member'
 	var reference := 'reference'
 	var ShadowedClass := 'ShadowedClass'
+	var base_variable_member
+	const base_function_member = 1
+	var base_const_member
 
 	print('warn')