chore(react-native-codegen): Remove fixtures and outdated transforms from build output (#49916)

Summary:
- Update ignore micromatch pattern to filter out `__test_fixtures__` from build output
- Remove `babel/plugin-transform-object-rest-spread`
- Remove `babel/plugin-transform-async-to-generator`
- Remove `babel/plugin-transform-destructuring`

The `package.json:engines:node` field is already set to `>=18` which makes the three Babel transforms that were removed redundant.

## Changelog:

[INTERNAL] [CHANGED] - Remove fixtures files and outdated Babel transforms from `react-native/codegen` build output

Pull Request resolved: https://github.com/facebook/react-native/pull/49916

Test Plan: - Ran against Node 18

Reviewed By: robhogan

Differential Revision: D70885090

Pulled By: cortinico

fbshipit-source-id: 328b75a6031a7ca6a9b3ed170061ffb0a47d6d93