class Server

Used to register for memory pressure level changes.

`watcher`: memory pressure `Watcher` channel that the `Provider` will use to send

level change messages to the client.

The current memory pressure level is immediately sent to the watcher

when this method is called.

It is recommended that the root job in a component tree register for changes,

rather than having individual jobs further down the tree register individually.

A low client count will help minimize system churn due to a large number of

memory pressure messages in transit at the same time.

Also, the more context a job has, the better equipped it will be to react to

memory pressure by controlling the behavior of children jobs in its tree.

|bind_handler| returns a handler that binds incoming connections to this

server implementation.

The returned handler borrows the server instance.

The server must outlive the provided |dispatcher|. Only after

the dispatcher is shutdown will it be safe to destroy the servers.

The server should not be moved.