Automatically add TileSet to TileMap

[KoBeWi]

godotengine/godot-proposals#1769 (comment)

[groud]

Thanks for the contribution! I would like to have a bit more people backing this proposal. I am not strictly against it but I see an annoying issue with it: Users might forget they are not working on their "common" TileSet and start to work on the automatically assigned TileSet. This might result in lost work as we have no way to merge two TileSet together.

I think I prefer the current situation a bit because, even if it's one step more to newcomers, it makes sure creating a new TileSet is what the users really wants. And also, when you build several maps, you should share TileSets quite often, so auto-assigning a new TileSet might not be the most useful.

[KoBeWi]

tbh I'm not convinced of this change either and #77962 already made it clear how to add a TileSet.
I only opened this PR because I thought there are no drawbacks, but you make a good point.

[KoBeWi]

Closing as this doesn't really bring any improvement. Most of the time you'll want to assign a TileSet file.