Use new dock system for TileMap and TileSet

[lodetrick]

See #113024

This PR updates the TileMap and TileSet docks to use the new dock system. Making the docks vertical in this PR ended up being a lot more complicated that I expected due to the nested controls, so I omitted it because it's important to get the simple implementation merged. I'm working on another PR that will add vertical support.

[KoBeWi]

The docks are visible at editor start, without any TileMap selected. You should probably close them after adding.

EDIT:
There is also some new error when folding TileSet resource in TileMapLayer's inspector:

editor/scene/2d/tiles/tile_set_editor.cpp:244 - Condition "tile_set.is_null()" is true.

[KoBeWi]

On a side note, we might want a separate editor setting for bottom tabs style 🤔

EDIT:
#113065

[lodetrick]

I decided to not fix the TileSet issue in this PR. After a few hours of digging, I realized it was a bigger issue with docks in general and I'm going to submit a separate PR that fixes it.

[Repiteo]

Thanks!