Remove circleci, old freebsd ci and vagrant (pkgeval) config files

[ViralBShah]

With the various recent upgrades to our infrastructure, we no longer use circleci, the old freebsd ci and vagrant (which was used for the old pkgeval).

@staticfloat Is it ok to delete the files in this PR?

[ViralBShah]

Can we also delete contrib/ackrc and its README? If people use it, we should move them to contrib/ack.

[staticfloat]

Can we also delete contrib/ackrc and its README? If people use it, we should move them to contrib/ack.

I would just move them now. I'm not sure how useful they are, but this is why we have a contrib/ directory.

[musm]

@ViralBShah you will also need to remove the section https://github.com/JuliaLang/julia/blob/master/README.md#vagrant

[ViralBShah]

I think the README itself needs refactoring. I will take a crack at it.

[musm]

Sounds good, but maybe in another PR ?

[ViralBShah]

I was planning to do it in this PR, but now that this is merged, @musm do you want to submit the PR? Otherwise I will get to it on sunday.

[StefanKarpinski]

I think the README itself needs refactoring.

It's pretty long. I wonder if it wouldn't be better to give a very high-level list of references to other locations where more detailed documentation of how to do various things can be found.

[ararslan]

I was planning to do it in this PR

My bad, didn't realize that was your intention.

[ViralBShah]

No worries. Now in #31858