add SceneTree's group methods in TileMapLayer

[galio17]

Describe the project you are working on

A metroidvania similar with Blasphemous

Describe the problem or limitation you are having in your project

Can't use groups when instantiate by TileMapLayer on TileSetScenesCollectionSource.
I want to move all the platforms using a button that calls a method on the group, but I want to take advantage of the flexibility of the tilemap to build the map using the TileSetScenesCollectionSource

Describe the feature / enhancement and how it helps to overcome the problem or limitation

Just adding the same group methods inside the TileMapLayer. So, I can call my group that is within the specific TileMapLayer, without searching for them in the TileSet

Describe how your proposal will work, with code, pseudo-code, mock-ups, and/or diagrams

Instead use get_tree(), calls a reference of the tilemap to use groups inside of them:

$TileMapLayer.call_group("platforms", "move")
$TileMapLayer.get_nodes_in_group()
$TileMapLayer.get_node_count_in_group()
...

If this enhancement will not be used often, can it be worked around with a few lines of script?

without the TileMapLayer, yeah. However, this would miss the point of why I wanted to use TileMapLayer, the ease of creating level designs

Is there a reason why this should be core and not an add-on in the asset library?

With the implementation of scenes in TileMapLayer, I believe that more developers will make this Node an important ally in map creation, leaving SceneTree responsible for creating the scenes used in it, while TileMapLayer is responsible for level design.