[Enh] Add ability to pull wrappers from heads instead of only tagged releases

[malucius-rh]

Feature request:
Add the ability for Zathras to pull wrappers from other than tagged releases.

For example:
Instead of only allowing:
location: https://github.com/redhat-performance/fio-wrapper/archive/refs/tags
exec_dir: "fio-wrapper-1.30/fio"
repo_file: "v1.30.zip"

Also allow something like:
location: https://github.com/redhat-performance/fio-wrapper/archive/refs/heads
exec_dir: "fio-wrapper-test/fio"
repo_file: fix_error_handling_typo.zip

This will allow Zathras-controlled runs using test/under development versions of wrappers without having to worry about risk to the main branch or keeping track of things like "is this a real v3.1.2 or a test v3.1.2?"