Look at system notes created just before merge as well as after, when deciding if an MR can be reverted

Closes #42377

See merge request gitlab-org/gitlab-ce!16678

On MySQL, at least, `Note#created_at` doesn't seem to store fractional seconds,
while `MergeRequest::Metrics#merged_at` does. This breaks the optimization
assumption that we only need to search for notes created *after* the MR has
been merged.

Unsynchronized system clocks also make this a dangerous assumption to make.

Adding a minute of leeway still optimizes away most notes, but allows both
cases to be handled more gracefully. If the system clocks are more than a
minute out, we'll still be broken, of course.

Add formatted_data attribute to Git::WikiPage

Closes #39805

See merge request gitlab-org/gitlab-ce!16682

Related to #39805

Use the DatabaseCleaner 'deletion' strategy instead of 'truncation'

Closes #30783

See merge request gitlab-org/gitlab-ce!16516

Resolve "Cannot change project visibility from Private (even when owner)"

Closes #40612

See merge request gitlab-org/gitlab-ce!16595