[wpilibc] Clean up include files (#2708)

Based on run of include-what-you-use.org to identify unused include files in various .h and .cpp files.

The changes mostly fall into 3 categories:
- Actually unused includes - copy-paste errors, not removing includes after cleaning up code, etc
- A too-broad include used where a more specific (and hopefully smaller) header will do
- Interface .h files including headers only needed by the .cpp implementation - moving from .h to .cpp
  will mean that code which uses the .h doesn't pay the price of processing the header file they don't need

wpilibc/src/main/native/cpp/Counter.cpp

@@ -13,6 +13,7 @@
 #include <hal/FRCUsageReporting.h>
 
 #include "frc/AnalogTrigger.h"
+#include "frc/Base.h"
 #include "frc/DigitalInput.h"
 #include "frc/WPIErrors.h"
 #include "frc/smartdashboard/SendableBuilder.h"