[TileMap] Fix forcing cleanup on exiting tree/canvas

[AThousandShips]

The code relies on that the deferred call is handled after the node exits the tree or canvas, this is because before the end of these notifications call both is_inside_tree and is_visible_in_tree retain the values they had before, so these changes being called immediately makes it not force cleanup properly

This feels like a pretty robust fix, and removes some unnecessary code, like the dedicated destructor flag, with the p_force_cleanup argument doing double duty here, I also moved the pending_update clearing to _internal_update, this avoids going through two other methods to reach the update (update_internals -> _deferred_internal_update -> _internal_update), while still catching any pending updates that might come after

Edit 2: Will write up a 4.2 dedicated version as this can't be cherry-picked directly, will open a PR for that when this is approved
Done, as the solution got a basic go-ahead and will wait on other changes in 4.3

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• Fixes: Tilemap light occluders affect all open scenes in the editor #89769

[Macksaur]

I tested this on my end, looks good!

[groud]

I prefer we merge #89179 first as it's a bigger change, but that looks like a correct fix to me. We can merge this PR afterwards.

[AThousandShips]

Agreed, just wanted a confirmation that it looks right, I'll rebase this on top of #89179 and fix the differences

Edit: Rebased and works well, will push once the layer expose has been merged

[akien-mga]

Thanks!

[AThousandShips]

Thank you!