ci(worker): fix broken ecs worker image version push

[bernardobridge]

Description

I just noticed that all image versions generated by AWS tests seem to be pointing to the main branch ref 💀 (https://github.com/artilleryio/artillery/actions/workflows/run-aws-tests.yml). I actually believe it is currently overriding the latest image in main. So the tests run against the right version of the code (which is why they pass), but the main branch image version gets overridden each time.

Important to fix ASAP.

P.S. This hasn't affected any production CLI release versions - fortunately there were pushes between each release and the next commit that had run-aws-tests each time.

Pre-merge checklist

• Does this require an update to the docs? No
• Does this require a changelog entry? No

[bernardobridge]

Note: due to usage of pull_request_target, this won't be reflected in workflows until it's in main - so we'll have to merge to test it.

[bernardobridge]

Note: 35c3ac4 increases test timeout temporarily due to failures observed in CI from cancellation (e.g. https://github.com/artilleryio/artillery/actions/runs/8099617233/job/22135921668).

These tests will be parallelised in PR's very soon, but in the meantime best to be generous with their runtime to prevent chasing CI failures that aren't relevant.

Chose to do it in this PR because once again changes to the workflow need to be in main to take effect, so might as well bundle it in this PR.