Use a complex workflow on Support scripts.

[Christian-B]

Depends on:
https://github.com/SpiNNakerManchester/SupportScripts/blob/main/.github/workflows/python_checks.yml
(I was too lazy to do that in a PR)

Have one complex workflow which can easily be reused.

If the SupportScripts workflow is change all that may be needed is to change the branch protection rules.

• As is the case here.

Based on:
SpiNNakerManchester/SpiNNMan#403

In the complex workflow does different things depending on the os and python version

1. for none ubuntu os it only does tests and what is needed for tests

• Current way other checks is ubuntu based
• I don't want to have to fight mutiple rules if the disagree by os

2. Most ubuntu also run flake8, pylint and mypy

• each python tested once (except the one used to validate)
• each ubuntu version tested once. latest used for remaining pythons
• These are then run before the test steps in 1 to see errors earlier
• One python version runs coverage

3. One ubuntu/ python also validate runs rat, sphinx and cff-validator

• this are run before the check steps in 2 and test steps 1 to see errors earlier

[rowleya]

Looks good - always happy to reduce the amount of copy-paste done!