Add flow definitions for fsPromise lstat and rm methods

Summary:
Add lstat() and rm() fsPromises methods, per:

* https://nodejs.org/docs/latest-v14.x/api/fs.html#fs_fspromises_lstat_path_options
* https://nodejs.org/docs/latest-v14.x/api/fs.html#fs_fspromises_rm_path_options

Reviewed By: panagosg7

Differential Revision: D32495063

fbshipit-source-id: da1059adda0a6e70182a69958bf498f1262dd009

lib/node.js

@@ -1296,6 +1296,7 @@ declare module "fs" {
   declare type EncodingOptions = { encoding?: string, ... };
   declare type EncodingFlag = EncodingOptions & { flag?: string, ... };
   declare type WriteOptions = EncodingFlag & { mode?: number, ... };
+  declare type RemoveOptions = { force?: boolean, maxRetries?: number, recursive?: boolean, retryDelay?: number, ... };
   declare class FileHandle {
     appendFile(data: string | Buffer, options: WriteOptions | string): Promise<void>;
     chmod(mode: number): Promise<void>;
@@ -1340,6 +1341,7 @@ declare module "fs" {
     lchmod(path: FSPromisePath, mode: number): Promise<void>,
     lchown(path: FSPromisePath, uid: number, guid: number): Promise<void>,
     link(existingPath: FSPromisePath, newPath: FSPromisePath): Promise<void>,
+    lstat(path: FSPromisePath): Promise<Stats>,
     mkdir(path: FSPromisePath, mode?: number | {
       recursive?: boolean,
       mode?: number,
@@ -1369,6 +1371,7 @@ declare module "fs" {
       & ((path: FSPromisePath, options: BufferEncoding) => Promise<Buffer>)
       & ((path: FSPromisePath, options?: string | EncodingOptions) => Promise<string>),
     rename(oldPath: FSPromisePath, newPath: FSPromisePath): Promise<void>,
+    rm(path: FSPromisePath, options?: RemoveOptions): Promise<void>,
     rmdir(path: FSPromisePath): Promise<void>,
     stat(path: FSPromisePath): Promise<Stats>,
     symlink(target: FSPromisePath, path: FSPromisePath, type?: 'dir' | 'file' | 'junction'): Promise<void>,