Add separate editor plugin for TileMap and TileSet

[KoBeWi]

Right now TilesEditorPlugin handles both TileMap and TileSet, which results in some errors when both are edited at the same time. Editing multiple objects is not supported; this PR adds separate dummy plugins for TileMap and TileSet, which just forward their methods to the original plugin.
It's a bit awkward, but it functions the same as before and doesn't spit errors.

I also added a note in EditorPlugin docs.

EDIT:
Fixes #74543

EDIT3:
Fixes #65467

[AThousandShips]

Is this a fix for #74543?

[akien-mga]

CC @groud

[groud]

I think this is a good thing to do. I think the implementation is OK but it's maybe too many layers right now, it becomes a bit complex.

I think we should probably remove TilesEditorPlugin and move functions related to TileMaps / TileSets in their respective plugin. For synchronization, we should probably have a TilesEditorSync singleton that would hold and forward the changes. Have you considered such an approach too ?

[KoBeWi]

Hmmm, now that I think about it, TilesEditorPlugin was a hack to allow 2 editors at once, but it's no longer necessary probably 🤔 Removing it might fix some bugs.

[KoBeWi]

Ok done. TilesEditorPlugin now handles some singleton things, but otherwise all editing is done by TileMapEditorPlugin and TileSetEditorPlugin. I had to resort to some tricks to make everything work correctly; I didn't do much testing though (yet).

[groud]

TilesEditorPlugin now handles some singleton things, but otherwise all editing is done by TileMapEditorPlugin and TileSetEditorPlugin

I think you can renames it then, to avoid any confusion. Something like TilesEditorSynchronizer or something.

[KoBeWi]

But the class does more than just synchronizing, so if anything, it needs a better name.

[groud]

But the class does more than just synchronizing, so if anything, it needs a better name.

Maybe TilesEditorsCommons? Or TilesEditorShared? TilesEditorHelper? TilesEditorHelpDesk? TilesEditorHotline? TilesEditorReferee? TilesEditorIDK 😅 ?

[KoBeWi]

Renamed to TilesEditorUtils.

[YuriSizov]

Superficially looks fine, but I'd still want an approval from @groud.

[groud]

I am not super convinced by the TileMapSubEditorPlugin name (maybe TileMapEditorTerrainsPlugin should maybe be TileMapSubEditorTerrainsPlugin, and same for TileMapEditorTilesPlugin ?). But it's a bit weird anyway.

Anyway, I'd rather have a better name but I agree it's a bit difficult to find. So I guess we I am in favor of YOLO-ing and it merge as is, as the code looks good anyway.

[KoBeWi]

These plugins are not exposed, so they can be renamed at any time.

[YuriSizov]

Thanks!

[AThousandShips]

Is this cherry pickable for 4.1? Or a variation of it? The issue appears to also occur there