remove GodotObject protocol

[mayoff]

It doesn't seem like the GodotObject protocol has any reason to exist. This patch removes it.

• The protocol has no requirements.

• There is exactly one directly conforming type: Object. All descendants of Object inherit the conformance, but any constraint requiring GodotObject conformance can be rewritten to instead require Object inheritance.

• There are three functions with GodotObject constraints:

  • VariantStorable.makeOrUnwrap
  • Variant.asObject
  • lookupObject

  All test cases pass if I change these constraints to require Object inheritance instead of GodotObject conformance.

[migueldeicaza]

Thank you for the contribution @mayoff - I agree with these changes.