CI workflow for Debian packaging

[bzed]

This PR adds github workflows to build Debian package.

Artifacts are not published yet, please decide if/how you want to handle this - they are stored in debian/artifacts in the workspace directory.

[alan-maguire]

I'm afraid the Oracle org has restrictions on enabling github actions, so I'm told actions like this are not permitted on github.com/oracle repos. Is there perhaps a way to create an associated "debian build" repo that can build the packages? thanks!

[bzed]

Thats really sad, unfortunately I don't know any useful way on github itself that wouldn't need github actions. On Debian's salsa we also can't mirror as its the free version of gitlab. I can do all that stuff on my private infrastructure, but thats far from optimal. To be honest I think that is an issue oracle needs to solve...

[alan-maguire]

On looking further it looks like we do actually have an approval process for GitHub actions; might take a while to work through it, but I'll report back once I've explored it more. Thanks!