FR: Reduce test workflow for each PR/commit

[bigtedde]

The problem

Our current Github test workflow has 38 checks being ran for each PR/commit. This uses a lot of resources and takes some time to complete.

Requested Solution

Our previous matrix strategy was 4 python versions (3.8 to 3.11) on 2 OS's (linux, mac), with one version of Borg (1.2.4). If we went back to this it would run these 8 checks for unit tests and 8 for integration tests, so 16 total (+ lint). This would reduce the workflow by about 58%. There would remain the option to run all 39 checks manually.

Alternatives

Open to feedback and alternatives 😀
@m3nu @real-yfprojects @jetchirag

Additional context

Addresses this comment.

[m3nu]

In favor of reducing default tests and running the rest only when merging into master or manually.

For the latest 2 PRs I've looked at, all had a test time out.

[real-yfprojects]

We could run integration tests with one python version only since borg should behave the same in every version while unit tests ensure that Vorta behaves the same in every python version. What do you think about that idea?

[real-yfprojects]

Also we can enable github's merge queue features which helps with merging multiple PRs after another while having to wait for ci each time.

For the latest 2 PRs I've looked at, all had a test time out.

Will reducing the test matric solve that? I would think some step in the workflow is taking too long if that problem occurs.