Add db field to connectionStatus command response

[chilagrow]

What should be done?

https://www.mongodb.com/docs/manual/reference/command/connectionStatus/#mongodb-data-connectionStatus.authinfo.authenticatedUserRoles-n-.db
FerretDB does not return db field in authenticatedUsers.

Where?

https://github.com/FerretDB/FerretDB/blob/main/internal/handler/msg_connectionstatus.go

Definition of Done

• handler updated;
• all backends updated;
• unit tests added/updated;
• integration/compatibility tests added/updated;
• spot refactorings done;
• user documentation updated or an issue to create documentation created;
• something else?

[rumyantseva]

It's a blocker for #1554.

Particularly, this check is needed: 910c351#diff-9c4603e660b20ed08f38491821f20d650d4a94d46ceb3f8ffe134549d62fc49cL171 and the info about db need to be stored in ConnInfo, so then it will be possible to use it to generate sessions hash.