GitHub Workflows security hardening (#34541)

Summary:
Signed-off-by: sashashura <[email protected]>

This PR adds explicit [permissions section](https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#permissions) to workflows. This is a security best practice because by default workflows run with [extended set of permissions](https://docs.github.com/en/actions/security-guides/automatic-token-authentication#permissions-for-the-github_token) (except from `on: pull_request` [from external forks](https://securitylab.github.com/research/github-actions-preventing-pwn-requests/)). By specifying any permission explicitly all others are set to none. By using the principle of least privilege the damage a compromised workflow can do (because of an [injection](https://securitylab.github.com/research/github-actions-untrusted-input/) or compromised third party tool or action) is restricted.
It is recommended to have [most strict permissions on the top level](https://github.com/ossf/scorecard/blob/main/docs/checks.md#token-permissions) and grant write permissions on [job level](https://docs.github.com/en/actions/using-jobs/assigning-permissions-to-jobs) case by case.

## Changelog

<!-- Help reviewers and the release process by writing your own changelog entry. For an example, see:
https://reactnative.dev/contributing/changelogs-in-pull-requests
-->

[Internal] [Added] - Explicit security permission definitions in autorebase workflow

Pull Request resolved: https://github.com/facebook/react-native/pull/34541

Reviewed By: cipolleschi

Differential Revision: D39544656

Pulled By: cortinico

fbshipit-source-id: 4918ee83fab7172a1d98689f10102fe2db2b17b7