### 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>();
	}
	
	RBSet<TerrainConstraint> output;
	output.insert(TerrainConstraint(this, p_position, p_terrains_pattern.get_terrain()));
	for (uint32_t i = 0; i < TileSet::CELL_NEIGHBOR_MAX; i++) {
		TileSet::CellNeighbor side = TileSet::CellNeighbor(i);
		if (tile_set->is_valid_terrain_peering_bit(p_terrain_set, side)) {
			TerrainConstraint c = TerrainConstraint(this, p_position, side, p_terrains_pattern.get_terrain_peering_bit(side));
			output.insert(c);
		}
	}
	return output;
}
RBSet<TileMap::TerrainConstraint> TileMap::_get_terrain_constraints_from_painted_cells_list(int p_layer, const RBSet<Vector2i> &p_painted, int p_terrain_set, bool p_ignore_empty_terrains) const {