Make 'automountServiceAccountToken' configurable - Issue #5290

What does this MR do?

Builds on the stale MR (!2143 (closed)) and adds chart-level support (as well as the initially proposed global support) for enabling / disabling service account token mounting.

Related issues

• Issue: #5290
• Original MR: !2143 (diffs)

Author checklist

Required

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• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com
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Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Tests added/updated
• Integration tests added to GitLab QA
• Equivalent MR/issue for omnibus-gitlab opened
• Equivalent MR/issue for Gitlab Operator project opened (see Operator documentation on impact of Charts changes)
• 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.