This ticket should involve adding a test to recreate the following error cases for calls to `WT_SESSION::drop`

• `WT_CONFLICT_BACKUP`: the table is currently performing backup

This ticket is part of a larger project SPM-3810, where the server should utilise the new api introduced in this project `WT_SESSION::get_last_error` to be able to handle these cases programatically. The `WT_SESSION::get_last_error` api has not been fully implemented yet, so a later ticket should modify the tests written in this ticket to ensure that the behaviour is correct.