Automate and streamline docker image generation

[baentsch]

Upon merge to "main" or when triggered by upstream build/release events, this project generates ready-made docker images at docker hub for users interested in "just using" OQS.

Currently, manual intervention right at the moment of completion of downstream CI is necessary to tag a specific docker image corresponding to a specific oqs-provider/liboqs release when the docker image has been created by CircleCI. If this moment is missed, the specific version needs to be manually created with the specific desired oqsprovider/liboqs version manually inserted to the Dockerfile(s) as subsequent CI runs overwrite the "latest" docker image. If using Github CI, a simple re-labeling of the correct commit is required as this commit ID is stored at docker hub (right now only for "openquantumsafe/openssl3").

This issue is to suggest streamlining and fully automating this:

• Generate docker images for all still supported OQS integrations via GH CI, moving away from CCI
• Upon an upstream GH release event, automatically tag the generated docker images with the upstream version ID

Tagging @ryjones fyi as I learned from @dstebila that you seem to know "everything github" and this issue may be straightforward for you to implement.