RFR: 7904004: Run jtreg GHA workflows for FreeBSD [v3]

[snake66]

> GitHub Actions does not natively support FreeBSD, so we use the vmactions/freebsd-vm action as a base to run the tests in a VM under an Ubuntu runner.
> 
> This work is sponsored by The FreeBSD Foundation.

snake66 has updated the pull request incrementally with one additional commit since the last revision:

  Use $(pwd) for path to checked out source dir

-------------

Changes:
  - all: https://git.openjdk.org/jtreg/pull/262/files
  - new: https://git.openjdk.org/jtreg/pull/262/files/d8f66b75..1e0623ce

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jtreg&pr=262&range=02
 - incr: https://webrevs.openjdk.org/?repo=jtreg&pr=262&range=01-02

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jtreg/pull/262.diff
  Fetch: git fetch https://git.openjdk.org/jtreg.git pull/262/head:pull/262

PR: https://git.openjdk.org/jtreg/pull/262