Run tests on linux and mac using also python 3.8 and 3.9

[ptormene]

This is just to trigger a full run of tests on linux

[micheles]

The tests here must run ONLY during the night, not at every pull request thus tripling the runtime without any good reason.

[ptormene]

Yes, my comment on top was cryptical, but what I meant was that I needed to open a draft PR in order to trigger the action right away and check that also python3.8 and 3.9 were ok. Then my intention is to have two very similar yml files, one running only on python3.10 at each PR (using -x) and one running also on 3.8 and 3.9 scheduled to run every night (without -x, so all errors are listed).

[ptormene]

Summarizing:

• at each PR, the workflow engine_pr_test (previously called engine_test) runs all tests on linux with python 3.10 only and using pytest -x to exit when the fist error occurs (see https://github.com/gem/oq-engine/actions/runs/6312398621)
• every night, a similar new workflow called engine_nightly_test runs all tests on linux with python 3.8, 3.9 and 3.10, using pytest without -x in order to identify all failures (see https://github.com/gem/oq-engine/actions/runs/6321221268)
• every night, also all tests and demos run on Windows (with python 3.10 only, see https://github.com/gem/oq-engine/actions/runs/6318741084/job/17158391732), Mac Intel (with python 3.8, 3.9 and 3.10, see https://github.com/gem/oq-engine/actions/runs/6320225038) and Mac M1 (with python 3.9.13 and 3.10.11, see https://github.com/gem/oq-engine/actions/runs/6319335089)

[micheles]

Ah, thanks @ptormene , then LGTM.