Bors-NG is deprecated, Bors-NG public instance is removed in the near feature

[Diman0]

https://bors.tech/newsletter/2023/05/01/tmib-76/
See the above blog.
The development of Bors-NG is feature frozen and deprecated.
The public Bors-NG instance we use is also deprecated. Somewhere in the future it will be taken down.

Before the public bors instance is taken down we have two options:

• Move to a self-hosted bors-ng instance.
• Move to something similar. For example the new github merge queue public beta

[nextgens]

I would prefer if we moved to GitHub merge queues

[Diman0]

I prefer this as well since bors-ng will not be maintained anymore.

The Github merge queue only partially takes care of the bors r+ part and does not offer anything for the bors try part. I will need to manually implement a new workflow that takes care of the CI/CD on pull request activities (bors try) and when we (or mergify) merges the PR which adds it to the merge queue (bors r+).

This should not be too difficult. It is a matter of adapting the workflows and testing it thoroughly.
I will first create something on my Mailu_Fork project that we can test.

As a bonus, we can automatically build images whenever a new commit is pushed to a PR branch. That will be handy 👍

[Diman0]

If the public bors instance goes down, we could use a self-hosted bors instance. I already set one up following the instructions on app.bors.tech.

You can see that it is working here:
Diman0/Mailu_Fork#22