src/vs/workbench/api/common/extHostMemento.ts/ExtensionMemento/keys
class ExtensionMemento:	keys(): readonly string[] {
		// Filter out `undefined` values, as they can stick around in the `_value` until the `onDidChangeStorage` event runs
		return Object.entries(this._value ?? {}).filter(([, value]) => value !== undefined).map(([key]) => key);
	}