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/NotifierCommand.h

@@ -37,7 +37,7 @@ class NotifierCommand : public CommandHelper<CommandBase, NotifierCommand> {
    * @param requirements the subsystems required by this command
    */
   NotifierCommand(std::function<void()> toRun, units::second_t period,
-                  std::initializer_list<Subsystem*> requirements);
+                  std::initializer_list<Subsystem*> requirements = {});
 
   NotifierCommand(NotifierCommand&& other);