[commands] Move GroupedCommands to CommandScheduler (#4728)

Move the command group checking functionality from CommandGroupBase into CommandScheduler.
Update references to grouping as composition for clarity (because explicitly grouping isn't the only way to do it).
Deprecate the static factory methods parallel, race, and deadline in CommandGroupBase in favor of the identical ones in Commands.

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

@@ -9,25 +9,17 @@
 #include <utility>
 
 #include "frc2/command/CommandBase.h"
-#include "frc2/command/CommandGroupBase.h"
 #include "frc2/command/CommandHelper.h"
 
 namespace frc2 {
 /**
- * Runs one of two commands, depending on the value of the given condition when
- * this command is initialized.  Does not actually schedule the selected command
- * - rather, the command is run through this command; this ensures that the
- * command will behave as expected if used as part of a CommandGroup.  Requires
- * the requirements of both commands, again to ensure proper functioning when
- * used in a CommandGroup.  If this is undesired, consider using
- * ScheduleCommand.
+ * A command composition that runs one of two commands, depending on the value
+ * of the given condition when this command is initialized.
  *
- * <p>As this command contains multiple component commands within it, it is
- * technically a command group; the command instances that are passed to it
- * cannot be added to any other groups, or scheduled individually.
- *
- * <p>As a rule, CommandGroups require the union of the requirements of their
- * component commands.
+ * <p>The rules for command compositions apply: command instances that are
+ * passed to it are owned by the composition and cannot be added to any other
+ * composition or scheduled individually, and the composition requires all
+ * subsystems its components require.
  *
  * This class is provided by the NewCommands VendorDep
  *