resharding_coordinator.cpp is an incredibly intense file to compile.
It takes at least 5 minutes to compile it, and it's often the long pole in a parallel build.

I've noticed that it depends on far too many headers.

It takes over 40 seconds to compile an empty (!!) .cpp file containing only the include block from resharding_coordinator.cpp. This should be trimmed.

However, without doing any thinking at all, we can bring the total compile time to under 60 seconds by physically breaking resharding_coordinator.cpp into multiple files.

This is a server-wide quality of life issue, so I'll give this a try as a Server Programmability task.