SceneTreeFTI - Fix force_update flag getting out of sync with invisible nodes

[lawnjelly]

…isible nodes

If the force_update flag remained set after the node was removed from the update lists, the node would never be updated in future. This could occur with hidden nodes that were moved after hiding.

Fixes #107142

Explanation

The SceneTreeFTI relies on node flags being in sync with nodes being on various update lists. This bug occurred for the forced frame update list, because the node flag was being cleared in the tree traversal, however invisible nodes were never having their flag cleared, and once the list was cleared the flag and the list became out of sync.

At further node movements, the logic determined incorrectly that the node was already on the update list.

We fix it by removing the flag manually on every node in the list rather than at traversal time.

Notes

• It's possible this can be done in a more optimal way at a later stage, but this shouldn't be bad.
• Also applicable in 3.x.
• I also corrected a few lines that didn't compile with GODOT_SCENE_TREE_FTI_EXTRA_CHECKS defined (these are compiled out of the main build, and are only there for regression testing, hence why CI didn't pick up before, they had some renames needed from 3.x version).

[lawnjelly]

I've flagged the usual suspects for review, but actually this is very straightforward, so anyone is welcome to review. 👍

[Ivorforce]

Rubber stamping this.
Code looks good to me; I don't fully understand how FTI works so I can't review the logic. But if Lawnjelly says it's needed for Beta, I don't see a reason not to merge this.

[lawnjelly]

Thanks @Ivorforce , if you can, can you approve #107178 too (which is the 3.x version) and I'll get that merged so it can get more testing.

[akien-mga]

Thanks!