Draft: Switched the qa job in charts to pull qa image using the revision tag unless its nil, in which case it'll use the nightly tag

What does this MR do?

By default, CNG uses nightly QA image in pipelines unless ['appVersion'] is specified in values. This can lead to out of sync issues between target env and QA image. The issue is to explore if GitLab version can be extracted from test Chart deployment and then passed to GitLab QA.

This MR fetches the Revision number of the app and uses that to pull the qa image. If the revision is empty, it'll use the nightly image for testing.

Related issues

gitlab-org/quality/quality-engineering/team-tasks#1562 (closed)

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion.

Required

• Merge Request Title and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com
• When ready for review, MR is labeled "~workflow::ready for review" per the Distribution MR workflow

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Tests added
• Integration tests added to GitLab QA
• Equivalent MR/issue for omnibus-gitlab opened
• Validate potential values for new configuration settings. Formats such as integer 10, duration 10s, URI scheme://user:passwd@host:port may require quotation or other special handling when rendered in a template and written to a configuration file.