Fix mason test not working when make install is used

[jabraham17]

Fixes an issue where mason was using the wrong CHPL_HOME path.

Previously, mason relied on a CHPL_HOME embedded in the binary. This was used to run tests via mason test. However, with make install CHPL_HOME would be different at build time versus install time.

This PR resolves the issue by having mason use the following for CHPL_HOME.

1. if the env var CHPL_HOME is set, use that
2. if chpl is available in PATH, use the CHPL_HOME from that (as reported by --print-chpl-home)
3. otherwise, fallback to the previous CHPL_HOME definition (from ChplConfig).

This PR also adds a step to our packaging configs to exercise mason test to ensure it continues to work.

Resolves #25356

[Reviewed by @benharsh]