The non-NT portion has been moved to wpiutil.
The NT portion has been moved to ntcore (as NTSendable).
SendableBuilder similarly split and moved.
SendableRegistry moved to wpiutil.
In C++, SendableHelper also moved to wpiutil.
This enables use of Sendable from wpimath and also enables
moving several classes from wpilib to wpimath.
This reverts commit a79faace1b.
This change will be superseded in a non-breaking way by changing to static functions and deprecating GetInstance() entirely.
Improves consistency across all classes.
Affects Preferences, LiveWindow, and CameraServer.
Old commands Scheduler::GetInstance() was not updated as this is already
deprecated.
This makes code easier to read and more consistent between C++ and Java.
Also update clang-format settings to always add a line break (even if no braces are used).
