Add missing Projection constructor with 16 real_t values

[aaronfranke]

When GDExtension generates bindings, it creates C++ code based on the API JSON. Values are serialized into literals constructed with numbers matching the value, for example, Vector3(0, 1, 0). This includes default values for function parameters. Projection default values are serialized like Projection(1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1). However, Godot is missing a constructor for Projection, so the generated C++ code doesn't compile:

I encountered this problem when the CI checks for godot-cpp failed to compile with my 4D module, because one of the bound methods includes a Projection default value, which cannot be constructed, as seen in the above image. This wasn't a problem in the engine before because the engine doesn't have any Projection default values in parameters.

See also PR which adds this to the engine: godotengine/godot#104113