Add functional-testing job

Description

Link to related ticket: https://repo1.dso.mil/groups/ironbank-tools/containers/-/epics/3

Testing:

• https://code-ib-zelda.staging.dso.mil/dsop/functional-testing/apache2/-/jobs/252982 (What a failing job will look like)
• https://code-ib-zelda.staging.dso.mil/dsop/functional-testing-bbimages/all-in-one/-/jobs/252996 (What a passing job will look like)

The job can't execute without the presence of a testing_manifest.yaml file in the project.

The job will be multi-arch after an arm64 runner is created.