[commands] Remove deprecated classes and functions (#5409)

Removes:
- PerpetualCommand
- Command.perpetually()
- CommandGroupBase
- Command.IsGrouped() (C++ only)
- Command.SetGrouped() (C++ only)
- Command.withInterrupt()
- ProxyScheduleCommand
- Button
- InternalButton, JoystickButton, NetworkButton and POVButton now subclass Trigger
- Old style Trigger functions:
    - Trigger.whenActive
    - Trigger.whileActiveOnce
    - Trigger.whileActiveContinuous
    - Trigger.whenInactive
    - Trigger.toggleWhenActive
    - Trigger.cancelWhenActive
- CommandScheduler.clearButtons()
- CommandScheduler.addButtons() (Java only)
- Command supplier constructor of SelectCommand

wpilibNewCommands/src/main/native/cpp/frc2/command/Command.cpp

@@ -11,7 +11,6 @@
 #include "frc2/command/ParallelCommandGroup.h"
 #include "frc2/command/ParallelDeadlineGroup.h"
 #include "frc2/command/ParallelRaceGroup.h"
-#include "frc2/command/PerpetualCommand.h"
 #include "frc2/command/RepeatCommand.h"
 #include "frc2/command/SequentialCommandGroup.h"
 #include "frc2/command/WaitCommand.h"
@@ -54,10 +53,6 @@ CommandPtr Command::WithInterruptBehavior(
   return std::move(*this).ToPtr().WithInterruptBehavior(interruptBehavior);
 }
 
-CommandPtr Command::WithInterrupt(std::function<bool()> condition) && {
-  return std::move(*this).ToPtr().Until(std::move(condition));
-}
-
 CommandPtr Command::BeforeStarting(
     std::function<void()> toRun,
     std::initializer_list<Subsystem*> requirements) && {
@@ -82,12 +77,6 @@ CommandPtr Command::AndThen(std::function<void()> toRun,
   return std::move(*this).ToPtr().AndThen(std::move(toRun), requirements);
 }
 
-PerpetualCommand Command::Perpetually() && {
-  WPI_IGNORE_DEPRECATED
-  return PerpetualCommand(std::move(*this).TransferOwnership());
-  WPI_UNIGNORE_DEPRECATED
-}
-
 CommandPtr Command::Repeatedly() && {
   return std::move(*this).ToPtr().Repeatedly();
 }
@@ -150,14 +139,6 @@ void Command::SetComposed(bool isComposed) {
   m_isComposed = isComposed;
 }
 
-bool Command::IsGrouped() const {
-  return IsComposed();
-}
-
-void Command::SetGrouped(bool grouped) {
-  SetComposed(grouped);
-}
-
 namespace frc2 {
 bool RequirementsDisjoint(Command* first, Command* second) {
   bool disjoint = true;