NavigationPolygon: Implement get/set_polygon fast paths.

[libklein]

Follow up to PR #92955. This PR implements the changes outlined in #92955 (comment).

As a first step, it implements fast-path get/set_polygons and get/set_outlines functions, updating NavMeshGenerator2D accordingly. Implemented get/set_polygons for NavigationMesh as well, replacing add_polygon whenever a direct update was preferable.

[smix8]

Needs both a rebase for 4.4 and the newer thread locks added to the functions.

[libklein]

Rebased onto the latest master:

• added read/write locks where appropriate

[libklein]

I've added two commits. d121458 addresses the issues you've outlined.

53d5b05 adds a overload to set_data that allows to set vertices, polygons, and outlines simultaneously in a thread safe way. Moreover, it avoids a for loop in get/set_data. Happy to push that to a different PR/revert if required.

[smix8]

Thank! Looks fine. I dont have any objection against the overload, that at least makes it clear that this function should never get exposed by accident.

[akien-mga]

Looks good! Could you squash the commits? See PR workflow for instructions.

[akien-mga]

Something went wrong with your rebase, which seemed to have amended changes into an unrelated merge commit from the master branch:

I fixed it for you by resetting to the previous commit (53d5b05) and just running git rebase -i upstream/master (with upstream pointing at godotengine/godot and up to date), and marking commits 2 to 5 as fixup.

[akien-mga]

Thanks!

[libklein]

Thank you! Is there any other issue I could assist with?