Breaking: Use named exports in metro-babel-register (#52564)

Summary:
Pull Request resolved: #52564

Currently, `metro-babel-register` has a function as its default export, to which we've tagged on various properties.

This tidies that up to a more idiomatic object of named exports, with `register` as a new one of them.

This also serves to make it more compatible with automatic TypeScript generation.

This is semver breaking, but `metro-babel-register` has very little usage outside Meta projects so isn't expected to be disruptive.

Changelog: [Internal]

Metro changelog:
```
 - **[Breaking]**: Move metro-babel-register's main function to a named export `register`
```

Reviewed By: huntie

Differential Revision: D78157559

fbshipit-source-id: c59c9820e9895007345561fed9ccec2273b925c8

Author: robhogan

scripts/shared/babelRegister.js

@@ -41,7 +41,15 @@ function registerForMonorepo() {
     // $FlowExpectedError[cannot-resolve-module] - Won't resolve in OSS
     require('@fb-tools/babel-register');
   } else {
-    require('metro-babel-register')([
+    // Temporarily allow the default export to be a function (Metro <= 0.82),
+    // or contain a `register` function (Metro >= 0.83). Remove shim once Metro
+    // is bumped in OSS.
+    const metroBabelRegister = require('metro-babel-register') /*:: as $FlowFixMe */;
+    const registerFunction =
+      typeof metroBabelRegister.register === 'function'
+        ? metroBabelRegister.register
+        : metroBabelRegister;
+    registerFunction([
       PACKAGES_DIR,
       PRIVATE_DIR,
       SCRIPTS_DIR,