configurable settings for liveness and readiness probes

What does this MR do?

Coincides with charts/auto-deploy-app!19 (merged) The point of this is to pass into the exposed variables for the livenessprobe and readinessprobe to make them configurable, since not all applications will serve a 200 on the root ("/") and/or the root ("/") may not be the appropriate health check for the application.

This is being submitted as a supplement to charts/auto-deploy-app!19 (merged) which is more important. Exhibiting how to test/exercise that code is the initial point here. If this is the proper way forward then I will work on the checklist below, however would prefer feedback on the original helm chart issue first.

What are the relevant issue numbers?

charts/auto-deploy-app!19 (merged) https://gitlab.com/gitlab-org/gitlab-ce/issues/46536

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• [-] Tests added for this feature/bug
• [-] Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• [-] Conforms to the database guides
• [-] Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• [-] Security reports checked/validated by reviewer