### 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 (atlas_source) {
				
				TileData *tile_data = atlas_source->get_tile_data(cell.get_atlas_coords(), cell.alternative_tile);
				if (tile_data && tile_data->get_terrain_set() == p_terrain_set) {
					current_pattern = tile_data->get_terrains_pattern();
				}
			}
		}
		TileSet::TerrainsPattern pattern = _get_best_terrain_pattern_for_constraints(p_terrain_set, coords, constraints, current_pattern);
		
		RBSet<TerrainConstraint> new_constraints = _get_terrain_constraints_from_added_pattern(coords, p_terrain_set, pattern);
		for (const TerrainConstraint &E_constraint : new_constraints) {
			if (constraints.has(E_constraint)) {
				constraints.erase(E_constraint);
			}
			TerrainConstraint c = E_constraint;
			c.set_priority(5);
			constraints.insert(c);
		}
		output[coords] = pattern;
	}
	return output;
}
HashMap<Vector2i, TileSet::TerrainsPattern> TileMap::terrain_fill_connect(int p_layer, const Vector<Vector2i> &p_coords_array, int p_terrain_set, int p_terrain, bool p_ignore_empty_terrains) {
	HashMap<Vector2i, TileSet::TerrainsPattern> output;
	ERR_FAIL_COND_V(!tile_set.is_valid(), output);
	ERR_FAIL_INDEX_V(p_terrain_set, tile_set->get_terrain_sets_count(), output);
	
	Vector<Vector2i> can_modify_list;
	RBSet<Vector2i> can_modify_set;