Port over CI work from freebsd/atf

[ngie-eign]

This change takes the CI work from the atf project that's been incubated and iterated on over the past several weeks/months.

This work enables CI workflows with FreeBSD on Cirrus CI with working/supported image families and with macOS/Ubuntu Linux on GitHub Actions.

Much of this work was done in collaboration with and building on work started by @kevemueller and @mchoo7 in that respective repo.