Review CODEOWNERS approvals by Verify maintainers

More than a year has passed since we last reviewed the devopsverify maintainer review requirements.

When looking at the reviewer roulette today, there's 8 of 14 maintainers available. Though one of them is Drew, who probably shouldn't be listed anymore in the Acting EM role. Verify maintainers frequently report a signficant amount of work goes into these reviews, while the value is not always clear.

What can we do here to improve?

Some suggestions:

• Narrow the policies / CODEOWNERS rules
• Train additional maintainers
• Clarify guidance to allow "rubberstamping" when appropriate
• Gather better data (look at review load and separate out backend / Verify maintainer)
• Leverage Duo (for example having it analyze Verify reviews to estimate when a Verify review is going to be impactful; or determine who reviewed relevant areas of the code before to suggest a more efficient match)
• … your ideas!

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See also: [Gitlab-Org] Improve Review Requirement Efficiency (#474654)