Run the macOS docker-related tests on the CI

[almet]

At the moment, the macOS tests are using the dummy provider. Because it seems possible to run Docker Desktop on the macOS runners, we could do so and run the docker-related tests as well on ARM64 and Intel.

Comments mention that "it takes around 10mn" to install, so we might want to cache this somehow.

[almet]

After some more investigation, it doesn't seem to be doable, because Nested Virtualization is not currently possible on the github runners, as mentioned here:

Nested-virtualization and Metal Performance Shaders (MPS) are not supported due to the limitation of Apple's Virtualization Framework.
— source

Some users report they have been able to run colima, but we've had issues with colima ourselves, and it's currently not a supported container runtime for Dangerzone.

The last option I see here is to rely on external dedicated action runners, like this.

[apyrgio]

Resolved as part of #1225, which will be soon pushed to main.