### Godot version

v4.0.beta11.official [91713ced8]

### System information

MX Linux 21

### Issue description

In Godot 3, TileMap had methods get_used_cells() and get_used_cells_by_id(). Godot 4's TileMap only has get_used_cells() and is missing get_used_cells_by_id().

get_used_cells_by_id() is highly useful in multiple cases, for example when trying to get all cells that are of road type, to randomly spawn a car.

Re-implementing get_used_cells_by_id() should be simple. The method could simply call get_used_cells(), and ignore all cells that are of the wrong ID.

### Steps to reproduce

N/A

### Minimal reproduction project

N/A
if (!tile_set.is_valid()) {
		return RBSet<TerrainConstraint>();
	}
	ERR_FAIL_INDEX_V(p_terrain_set, tile_set->get_terrain_sets_count(), RBSet<TerrainConstraint>());
	ERR_FAIL_INDEX_V(p_layer, (int)layers.size(), RBSet<TerrainConstraint>());
	
	RBSet<TerrainConstraint> dummy_constraints;
	for (const Vector2i &E : p_painted) {
		for (int i = 0; i < TileSet::CELL_NEIGHBOR_MAX; i++) { 
			TileSet::CellNeighbor bit = TileSet::CellNeighbor(i);
			if (tile_set->is_valid_terrain_peering_bit(p_terrain_set, bit)) {
				dummy_constraints.insert(TerrainConstraint(this, E, bit, -1));
			}
		}
	}
	
	RBSet<TerrainConstraint> constraints;