### Godot version

v4.0.3.stable.mono.official [5222a99f5]

### System information

macOS Monterey 12.6.6 (21G646)

### Issue description

When creating a tileset by code with custom data layers, removing a layer with `remove_custom_data_layer` does not update the name-to-layer mapping; `get_custom_data_layer_by_name` will continue to return that layer's original index.

This has a downstream effect of causing TileData objects attempting to use `get_custom_data('Layer B')` to return invalid data (whatever custom data is now in Layer B's old index; e.g. Layer C).

I would expect that after using `remove_custom_data_layer`, I would be able to still use `get_custom_data_layer_by_name` on that tileset.

### Steps to reproduce

Run this code to see that getting Layer B by name after removing the first layer continues to return its original index (1) when in reality it is now at index 0.
```
	var tileset:TileSet = TileSet.new()

	tileset.add_custom_data_layer()
	tileset.set_custom_data_layer_name(0, 'Layer A')
	tileset.set_custom_data_layer_type(0, TYPE_INT)

	tileset.add_custom_data_layer()
	tileset.set_custom_data_layer_name(1, 'Layer B')
	tileset.set_custom_data_layer_type(1, TYPE_STRING)

	print('Layer index 0 name : ', tileset.get_custom_data_layer_name(0)) # Layer A
	print('Layer index 1 name : ', tileset.get_custom_data_layer_name(1)) # Layer B
	print('Layer B is on index : ', tileset.get_custom_data_layer_by_name("Layer B")) # 1

	print('----- removing custom data layer 0 -----')
	tileset.remove_custom_data_layer(0)

	print('Layer index 0 name : ', tileset.get_custom_data_layer_name(0)) # Layer B
	print('Layer index 1 name : ', tileset.get_custom_data_layer_name(1)) # prints an error, as expected
	print('Layer B is on index : ', tileset.get_custom_data_layer_by_name("Layer B")) # returns 1 still! should return 0.
```

### Minimal reproduction project

[RemoveCustomDataLayer.zip](https://github.com/godotengine/godot/files/11804762/RemoveCustomDataLayer.zip)

return next_source_id;
}
void TileSet::_update_terrains_cache() {
	if (terrains_cache_dirty) {
		
		per_terrain_pattern_tiles.resize(terrain_sets.size());
		for (RBMap<TileSet::TerrainsPattern, RBSet<TileMapCell>> &tiles : per_terrain_pattern_tiles) {
			tiles.clear();
		}
		for (const KeyValue<int, Ref<TileSetSource>> &kv : sources) {
			Ref<TileSetSource> source = kv.value;
			Ref<TileSetAtlasSource> atlas_source = source;
			if (atlas_source.is_valid()) {
				for (int tile_index = 0; tile_index < source->get_tiles_count(); tile_index++) {
					Vector2i tile_id = source->get_tile_id(tile_index);
					for (int alternative_index = 0; alternative_index < source->get_alternative_tiles_count(tile_id); alternative_index++) {
						int alternative_id = source->get_alternative_tile_id(tile_id, alternative_index);
						
						TileData *tile_data = atlas_source->get_tile_data(tile_id, alternative_id);
						int terrain_set = tile_data->get_terrain_set();
						if (terrain_set >= 0) {
							TileMapCell cell;
							cell.source_id = kv.key;
							cell.set_atlas_coords(tile_id);
							cell.alternative_tile = alternative_id;
							TileSet::TerrainsPattern terrains_pattern = tile_data->get_terrains_pattern();
							
							if (terrains_pattern.get_terrain() >= 0) {