Auto-build Docker images before on-merge if setup.py was changed
# What does this PR do?

This PR introduces a new workflow that will check if the `setup.py` was modified during a pull request merge. If so, it will trigger the docker images to be rebuilt before running the `on-merge` tests. 

It also changes `self-push` to be ran on a `workflow_run`, specifically the new `check-dependencies` job. This new job also maintains the same "on-merge" check the previous job had, when it comes to determining if it should be ran and when.

Finally, `build-docker-images` is now also ran on a `workflow_call`, so that `check-dependencies` can trigger it. 

This is the same as done in Accelerate recently, with the only difference being additional file filters https://github.com/huggingface/accelerate/pull/424

## Why is this needed? 

A frustration I've noticed over the last few months in this repo is the main tests runners are failing for an entire day, due to a new dependency introduced. This solves this problem, since the issue roots from the docker images being used.

## Before submitting
- [ ] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
- [x] Did you read the [contributor guideline](https://github.com/huggingface/transformers/blob/main/CONTRIBUTING.md#start-contributing-pull-requests),
      Pull Request section?
- [ ] Was this discussed/approved via a Github issue or the [forum](https://discuss.huggingface.co/)? Please add a link
      to it if that's the case.
- [ ] Did you make sure to update the documentation with your changes? Here are the
      [documentation guidelines](https://github.com/huggingface/transformers/tree/main/docs), and
      [here are tips on formatting docstrings](https://github.com/huggingface/transformers/tree/main/docs#writing-source-documentation).
- [ ] Did you write any new necessary tests?


## Who can review?

Anyone in the community is free to review the PR once the tests have passed. Feel free to tag
members/contributors who may be interested in your PR.

@ydshieh @LysandreJik 
_The documentation is not available anymore as the PR was closed or merged._<|||||>Do not merge for now. The push CI in transformers is somehow tricky, after the recent change in #17369.
I will review tomorrow, but I think some changes have to be made.<|||||>@muellerzr Thank you for the PR. 

The most direct approach would be

Integrate the check `check-for-setup` and `build-docker-containers` in  
https://github.com/huggingface/transformers/blob/main/.github/workflows/self-push-caller.yml
(before the job `run_push_ci`)

Otherwise (if you really want to keep the logic you have), the following block
```
  workflow_run:
    workflows: ["Check for dependency modification"]
    branches: ["main"]
    types: [completed]
```
should go in `self-push-caller.yml`.

The main point is to run the actual push CI tests on another branch (`push-ci`), otherwise there will be more than 256 job results shown in the commit history page.

I would prefer the most direct approach (the first one).<|||||>@ydshieh I *believe* I addressed what you wanted, let me know if otherwise 😄 