Add requirements param to more Command APIs (#2059)

Assorted improvements to the ergonomics of declaring requirements in the new
command framework. C++ requirements list parameters have been defaulted
to an empty list, some missing C++ requirements list parameters have been
added, and both C++ and Java have been given requirements list params in
various InstantCommand wrapper methods (#2049), whose value is
forwarded to the command.

wpilibNewCommands/src/main/native/include/frc2/command/PIDCommand.h

@@ -40,7 +40,7 @@ class PIDCommand : public CommandHelper<CommandBase, PIDCommand> {
              std::function<double()> measurementSource,
              std::function<double()> setpointSource,
              std::function<void(double)> useOutput,
-             std::initializer_list<Subsystem*> requirements);
+             std::initializer_list<Subsystem*> requirements = {});
 
   /**
    * Creates a new PIDCommand, which controls the given output with a