Remove the usage of docker buildx

[edmondchuc]

Docker Buildx is only required when creating multi-arch container images. Since we're not doing that here, it's better to not use it.

If we do use it, we have to set provenance = false in the docker/build-push-action step due to an issue with the image metadata when pushed to GitHub Container Registry. See docker/build-push-action#778 for context. This issue was introduced in v3.3.0 of docker/build-push-action.

[edmondchuc]

This PR is also bringing to light the recent release of SQLAlchemy v2's incompatibility with Flask-SQLAlchemy.

[gweis]

not quite as straightforward as updating Flask-SQLAlchemy .... Flask-SQLALchemy has been fixed last October. ... however that fix kinda came along with a requirement to update Flask to >= 2.2 (which we pin to < 2.1.0) ...
so ...either we pin sqlalchemy to < 3.0.0 or we update Flask to latest version ... either way should fix this dependency problem (I guess Flask 2.2 upgrade requires a bit of testing as well)

[gweis]

(and yes .. .this whole docker buildx, DOCKER_BUILDKIT=1, etc... is a bit messy, and depends too much on the builders available to your environment (IMO)