Goal
Remove the assumption there should always be a reader/writer TicketHolder. Transform the FIFOTicketHolder and SemaphoreTicketHolder classes to internally manage /separate their reader/writers.

In an Ideal world, we can have a single TicketHolder instance and get rid of the TicketHolders class altogether.

Context
Right now, the TicketHolders class expects there to always be a reader and writer TicketHolder class. However, for the FIFOTicketHolder, no real performance gain is tied to separating readers / writers.

SERVER-66152 introduces the SchedulingTicketHolder with n internal Queues to keep track of.