getUsedExports(module, runtime) {
		const mgm = this._getModuleGraphModule(module);
		return mgm.exports.getUsedExports(runtime);
	}
@param {Module} module the module
@param {RuntimeSpec} runtime the runtime
@returns {false | true | SortableSet<string> | null} the used exports
false: module is not used at all.
true: the module namespace/object export is used.
SortableSet<string>: these export names are used.
empty SortableSet<string>: module is used but no export.
null: unknown, worst case should be assumed.