[ci] fix how tactical retries work when build.yaml is changed

[cjllanwarne]

Change Description

Updates tactical retries to work properly with build.yaml changes.

Previously we had a gating check such that if all tests were being requested, the tactical retest request was being ignored. That's not quite the right semantics. We want all tests to be attempted, but if one has already passed there's no reason to re-run it, especially if the retry was requested tactically.

Therefore, for all tactical builds:

• Find all the steps which would have been added if we were running non-tactically. This becomes the base set of requested_steps set
• Check which already succeeded and remove them from the requested_steps
• Rebuild the test build configuration with the newly reduced set of requested steps

Security Assessment

• This change potentially impacts the Hail Batch instance as deployed by Broad Institute in GCP

Impact Rating

• This change has a low security impact

Impact Description

Small tweak to fix test step selection

Appsec Review

• Required: The impact has been assessed and approved by appsec