Split build workflow for multiple plateforms

[fxmarty]

As per title.

We may need other EC2 runners, or stop using them altogether, as it may be meaningless to launch multiple times the same AMI?

[Narsil]

Can't we keep a single file and making it parallel using strategy: matrix instead ?

[fxmarty]

We could indeed keep a single file and just remove the

    needs:
      - start-runner
      - build-and-push-image # Wait for the main docker image to be built
      - integration-tests # Wait for the main integration-tests

and use e.g.

runs-on: [self-hosted, tgi-builder] instead of AWS.