Add options to use configMaps and define keys for customCA

What does this MR do?

When defining custom CAs:

• Adds the option to use ConfigMaps in addition to Secrets.
• Adds the option to define specific keys to be mounted for both ConfigMaps and Secrets.

Related issues

Closes #3393 (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 N/A
• Equivalent MR/issue for omnibus-gitlab opened N/A
• 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.