Merge the nox jobs in one job that can be used for branch protection

[llucax]

What's needed?

We need to avoid having to update branch protection rules each time a new matrix item is added or removed from the nox job.

Proposed solution

Same as the cross-arch test jobs in the SDK:

https://github.com/frequenz-floss/frequenz-sdk-python/blob/d34aea674ee10363a3b99bb01d7b2d2b67d94a1d/.github/workflows/ci.yaml#L175-L188

If we make one nox job that depends on all the matrix jobs, then we can use that for branch protection so we don't need to update the protection rules each time the matrix is changed.

Use cases

No response

Alternatives and workarounds

No response

Additional context

SDK PR:

• [ci] Add tests for non-native architectures frequenz-sdk-python#622

[llucax]

This was done already.