Support fsevents watcher on Apple silicon (#875)

Summary:
If Watchman is unavailable or disabled, we try to fall back to `FSEventsWatcher` and then to `NodeWatcher`. `FSEventsWatcher` is only available on `darwin`, so we `require` it in a try/catch and swallow any error.

This was hiding the fact that `fsevents` was also failing to load on Apple silicon:
```
 dlopen(/Users/robhogan/gh/metro/node_modules/fsevents/fsevents.node, 0x0001): tried: '/Users/robhogan/gh/metro/node_modules/fsevents/fsevents.node' (mach-o file, but is an incompatible architecture (have (x86_64), need (arm64e)))
 ```

`fsevents@2.3` introduces support for Apple silicon. This updates to that version, and also adds Flow types based on the TypeScript types bundled with `fsevents` so that Flow check passes on `darwin` (the Flow error was `untyped-import` so the existing `cannot-resolve-module` suppression doesn't work).

Pull Request resolved: #875

Test Plan:
### After:
```
$ node packages/metro/src/cli serve -c ../dummyproj/metro.config.js

                        ▒▒▓▓▓▓▒▒
                     ▒▓▓▓▒▒░░▒▒▓▓▓▒
                  ▒▓▓▓▓░░░▒▒▒▒░░░▓▓▓▓▒
                 ▓▓▒▒▒▓▓▓▓▓▓▓▓▓▓▓▓▒▒▒▓▓
                 ▓▓░░░░░▒▓▓▓▓▓▓▒░░░░░▓▓
                 ▓▓░░▓▓▒░░░▒▒░░░▒▓▒░░▓▓
                 ▓▓░░▓▓▓▓▓▒▒▒▒▓▓▓▓▒░░▓▓
                 ▓▓░░▓▓▓▓▓▓▓▓▓▓▓▓▓▒░░▓▓
                 ▓▓▒░░▒▒▓▓▓▓▓▓▓▓▒░░░▒▓▓
                  ▒▓▓▓▒░░░▒▓▓▒░░░▒▓▓▓▒
                     ▒▓▓▓▒░░░░▒▓▓▓▒
                        ▒▒▓▓▓▓▒▒

                Welcome to Metro v0.72.3
              Fast - Scalable - Integrated

  Metro:FSEventsWatcher Watching /Users/robhogan/gh/dummyproj +0ms
```

Reviewed By: huntie

Differential Revision: D39883504

Pulled By: huntie

fbshipit-source-id: 223a390715f13f32cdc1788185c75a96433581de

flow-typed/fsevents.js

@@ -0,0 +1,73 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict
+ * @format
+ * @oncall react_native
+ */
+
+declare module 'fsevents' {
+  declare type Event =
+    | 'created'
+    | 'cloned'
+    | 'modified'
+    | 'deleted'
+    | 'moved'
+    | 'root-changed'
+    | 'unknown';
+
+  declare type Type = 'file' | 'directory' | 'symlink';
+
+  declare type FileChanges = {
+    inode: boolean,
+    finder: boolean,
+    access: boolean,
+    xattrs: boolean,
+  };
+
+  declare type Info = {
+    event: Event,
+    path: string,
+    type: Type,
+    changes: FileChanges,
+    flags: number,
+  };
+
+  declare type WatchHandler = (path: string, flags: number, id: string) => void;
+
+  declare type FSEvents = {
+    watch(path: string, handler: WatchHandler): () => Promise<void>,
+    getInfo(path: string, flags: number): Info,
+    constants: {
+      None: 0x00000000,
+      MustScanSubDirs: 0x00000001,
+      UserDropped: 0x00000002,
+      KernelDropped: 0x00000004,
+      EventIdsWrapped: 0x00000008,
+      HistoryDone: 0x00000010,
+      RootChanged: 0x00000020,
+      Mount: 0x00000040,
+      Unmount: 0x00000080,
+      ItemCreated: 0x00000100,
+      ItemRemoved: 0x00000200,
+      ItemInodeMetaMod: 0x00000400,
+      ItemRenamed: 0x00000800,
+      ItemModified: 0x00001000,
+      ItemFinderInfoMod: 0x00002000,
+      ItemChangeOwner: 0x00004000,
+      ItemXattrMod: 0x00008000,
+      ItemIsFile: 0x00010000,
+      ItemIsDir: 0x00020000,
+      ItemIsSymlink: 0x00040000,
+      ItemIsHardlink: 0x00100000,
+      ItemIsLastHardlink: 0x00200000,
+      OwnEvent: 0x00080000,
+      ItemCloned: 0x00400000,
+    },
+  };
+
+  declare module.exports: FSEvents;
+}

packages/metro-file-map/package.json

@@ -30,6 +30,6 @@
     "slash": "^3.0.0"
   },
   "optionalDependencies": {
-    "fsevents": "^2.1.2"
+    "fsevents": "^2.3.2"
   }
 }

packages/metro-file-map/src/watchers/FSEventsWatcher.js

@@ -8,6 +8,9 @@
  * @flow strict-local
  */
 
+// $FlowFixMe[cannot-resolve-module] - Optional, Darwin only
+import type {FSEvents} from 'fsevents';
+
 // $FlowFixMe[untyped-import] - anymatch
 import anymatch from 'anymatch';
 import EventEmitter from 'events';
@@ -19,10 +22,11 @@ import walker from 'walker';
 // $FlowFixMe[untyped-import] - micromatch
 const micromatch = require('micromatch');
 
+const debug = require('debug')('Metro:FSEventsWatcher');
+
 type Matcher = typeof anymatch.Matcher;
 
-// $FlowFixMe[unclear-type] - fsevents
-let fsevents: any = null;
+let fsevents: ?FSEvents = null;
 try {
   // $FlowFixMe[cannot-resolve-module] - Optional, Darwin only
   fsevents = require('fsevents');
@@ -116,12 +120,13 @@ export default class FSEventsWatcher extends EventEmitter {
     this.doIgnore = opts.ignored ? anymatch(opts.ignored) : () => false;
 
     this.root = path.resolve(dir);
-    this.fsEventsWatchStopper = fsevents.watch(
-      this.root,
-      // $FlowFixMe[method-unbinding] - Refactor
-      this._handleEvent.bind(this),
+
+    this.fsEventsWatchStopper = fsevents.watch(this.root, path =>
+      this._handleEvent(path),
     );
 
+    debug(`Watching ${this.root}`);
+
     this._tracked = new Set();
     FSEventsWatcher._recReaddir(
       this.root,