CI: Add release based containers

[syeopite]

• Changes the current master based container to use "master" tag instead of "latest" tag
• Adds a new workflow to build a container on each new release which has the "latest" tag, and a tag based on the current released version.

Once this process is done, it should allow us to quickly merge PRs which passed the code-review but not the testing stage. Instead, the testing-stage can be pushed to when each release occurs.

[iBicha]

Changes the current master based container to use "master" tag instead of "latest" tag

stable might be more commonly used/understood. Or even production.
Very good initiative!

[syeopite]

The release containers are tagged as "latest" as to ensure a smooth transition for instances.

As testing is being moved to per-release with this PR, instances should be using the release containers instead of the container built off master as to ensure instance stability.

[iBicha]

The release containers are tagged as "latest" as to ensure a smooth transition for instances.

As testing is being moved to per-release with this PR, instances should be using the release containers instead of the container built off master as to ensure instance stability.

Fair enough, I take my comment back

[SamantazFox]

Could you rename the two files to something in the odds of container-release and container-nightly (or whatever you see fit)? The two names are too similar, that's confusing!

[SamantazFox]

Marking as ready as the only option to trigger that is to merge the code and publish a new tagged release.