Need more frequent testing of non-Debian platforms

[epgts]

Currently we only test on Red Hat derived systems at release time, and we keep hitting surprises.

ci.yml is already parameterized, so we can already start doing better by running the ci tests manually on these platforms.

But we should do better, one step at a time:

1. Run ci.yml nightly for all the systems we release for.
2. Build timescaledev/toolkit-builder-nightly images every night.
3. Change the ci.yml nightly build to use last night's nightly image
4. Maybe even run tools/release in non-push form every night? Why not?

2 and 3 help us shake out bitrot in the infrequently-changing image. We've been hit at least twice before:

• we depend on bleeding-edge fpm and one day it required newer Ruby
• the gh deb we use disappeared