ci,buildsys: migrate the jobs on Travis-CI to GitHub Actions or somewhere

[masatake]

Travis-ci is too slow.

It might be better to consider using GitHub Actions.
Also, note that travis-ci.org will end this month. We should migrate to travis-ci.com if we still use Travis CI.
https://docs.travis-ci.com/user/migrate/open-source-repository-migration

Originally posted by @k-takata in #2757 (comment)

[masatake]

@k-takata, thank you for the critical notification.

I have already run a heavy (large?) job (make units VG=1) at GitHub. I'm afraid of becoming GitHub Actions a bottleneck.
Anyway, we have to migrate the jobs at Travis-CI.

[masatake]

I moved the most of all workloads run at Travis-CI to GitHub Actions.

[masatake]

We have used all credits. We have to move the remaining tests to Git Hub Actions.