To guarantee polymorphism, a method signature must be compatible with
the parent. This checks if:
1. Return type is the same.
2. The subclass method takes at least the same amount of parameters.
3. The matching parameters have the same type.
4. If the subclass takes more parameters, all of the extra ones have a
default value.
5. If the superclass has default values, so must have the subclass.
There's a few test cases to ensure this holds up.
This makes sure that assigning values to enum-typed variables are
consistent. Same enum is always valid, different enum is always
invalid (without casting) and assigning `int` creates a warning
if there is no casting.
There are new test cases to ensure this behavior doesn't break in
the future.
Inline getters & setters are now FunctionNodes.
Their names are set in the parser, not in the compiler.
GDScript-Analyzer will now run through getter and setter.
Also report wrong type or signature errors regarding getset properties.
Added GDScript tests for getters and setters.
#53102
