As part of SERVER-53935 we realized that DBDirectClient was unexpectedly modifying the readConcernArgs in the callers opCtx.

This ticket is to consider using an AlternativeClientRegion in DBDirectClient so that there is no possibility that the callers opCtx is modified unexpectedly. Instead, callers will need to explicitly transfer any state they wish for a client to inherit (e.g. readConcern, maxTimeMs)

Acceptance criteria:

DBDirectClient doesn't unexpectedly modify opCtx.