The hook RunDBCheckInBackground fails with CommandNotSupportedOnLegacyTimeseriesBucketsNamespace in FCV upgrade/downgrade tests when it races with the FCV change.

Currently we're checking FCV at collection-listing time, but FCV can change between listing and command execution, causing the server to reject the command on legacy system.buckets.

Instead of checking FCV, we should check if we're in multiversion mode, 8.3 binary can automatically translate the main timeseries namespace to system.buckets internally. In multiversion tests, we must check system.buckets because 8.0 binaries cannot do this translation and need the coverage.