CODEOWNERS: Add Stephane Rochoy

Stephane Rochoy isn't quite the maintainer of these items, but has an
interest in them. As an experiment, see if this is a viable thing to do.

MAINTAINERS: Add myself for nvme entries, remove jimharris

Jim Harris no longer has a commit bit and has moved on from being the
FreeBSD nvme driver maintainer at Intel. I've been reviewing things
so I'll take that up.

Sponsored by: Netflix

MAINTAINERS, etc: Remove hselasky entries

Sadly, Hans-Peter has passed away. Remove his entries out of respect for
his many years of service to the project.

MAINTAINERS: Add myself to stand

People email me when the boot loader breaks anyway, so ask to be
included in reviews. And ask strongly since I've had to deal with too
many major breakages lately, distruting other things I need to do.

Sponsored by: Netflix

MAINTAINERS+GitHub: Reflect ipfilter was moved from contrib to netpfil

Reflect the fact that ipfilter was moved from contrib to netpfil
on December 20, 2021 by 3b9b51fe464e. And that ipfilter userland
was moved from contrib to sbin/ipf by 41edb306f056 that same day.

Add myself to the github code owners file

GitHub: Add libefivar's path to CODEOWNERS

Code owners are automatically requested for review when someone opens a
pull request that modifies code that they own.

https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/about-code-owners

Pull Request: https://github.com/freebsd/freebsd-src/pull/581

[skip ci] fix syntax in CODEOWNERS

* Fix invalid usernames
- Fix spelling of ngie-eign
- Delete users who aren't members of the FreeBSD org
* Fix spelling of usr.bin/fetch in CODEOWNERS
* rm "a directory anywhere in the repo" patterns from CODEOWNERS
Even though they're documented as working, in practice they don't.
https://docs.github.com/en/github/creating-cloning-and-archiving-repositories/creating-a-repository-on-github/about-code-owners#codeowners-file-location

MFC after: 2 weeks
Sponsored by: Axcient
Reviewed by: imp
Differential Revision: https://reviews.freebsd.org/D30849

[skip ci] volunteer to maintain POSIX AIO

MFC after: 2 weeks

[skip ci] add a CODEOWNERS file

Summary:
Convert MAINTAINERS into a Github CODEOWNERS file. This will
automatically assign reviewers to some GH pull requests. The conversion
is not 1:1; some committers don't have Github accounts (e.g. adrian),
some functional areas don't neatly correspond to a set of files (e.g.
kqueue), and mailing lists can't be assigned as a reviewer (e.g.
secteam@). But it's a start.

MFC after: 2 weeks
Reviewed by: imp
Differential Revision: https://reviews.freebsd.org/D30559