Improving contributor experience for "trusted" users -- faster CI by using self-hosted runners

[Ash Berlin-Taylor]

Hi all,

I'd like to propose we start allowing more users to use the self-hosted 
runners -- they are much much quicker to run test workflows. And by 
making promising people's tests run quicker hopefully we can encourage 
them to make more PRs and continue on the path towards becoming a 
committer.

Currently only committers and PMC members test builds are run using the 
self-hosted runners, everyone else has to use the GitHub public 
runners. The "stuck in queue" issue doesn't plague us much anymore (I 
think?), but the main issue is still that the GitHub runners only have 
8GB vs the 64GB of the self-hosted (half of which is used as RAM FS) 
and as a result they are much, much slower.

So I propose that we "allow users we trust" to run on the self-hosted 
runners. This is purposefully a lighter weight process than adding 
those users to the Triage group (which we need to have a "vote"/mailing 
list for and then ask ASF Infra team to make the changes to) and is 
essentially a way to make the contributing process nicer for those that 
have shown interest and promise.

I am thinking that this would often be used for "this person is making 
a number of good quality PRs, and is on the road to being a committer".

In terms of project process, all I'm envisaging is that this requires a 
PR to add someone's GitHub username to 
<https://github.com/apache/airflow/blob/366c66b8f6eddc0d22028ef494c62bb757bd8b8b/.github/workflows/ci.yml#L80-L123> 
and then the "normal" review process to get the change merged.

By adding a user to that list the committer/PMC member is saying "I am 
sponsoring this user and trust them to not be malicious".

There will be a bit more work to finish this off, namely we'll need to 
get <https://github.com/apache/airflow-ci-infra/pull/20> finished and 
working.

We should probably be aware that if we do this it will likely be 
"people we (committers) work with" in the first instance. Are we okay 
with that, even if they haven't yet contributed (much/at all) to 
Airflow?

Are there any other criteria that people thing we should apply before 
adding users to this list?

Thoughts?