[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/test/native/cpp/frc2/command/button/TriggerTest.cpp

@@ -3,7 +3,6 @@
 // the WPILib BSD license file in the root directory of this project.
 
 #include <frc/simulation/SimHooks.h>
-#include <wpi/deprecated.h>
 
 #include "../CommandTestBase.h"
 #include "frc2/command/CommandPtr.h"
@@ -207,24 +206,6 @@ TEST_F(TriggerTest, Negate) {
   EXPECT_TRUE(scheduler.IsScheduled(&command));
 }
 
-// this type of binding is deprecated and identical to OnTrue
-WPI_IGNORE_DEPRECATED
-TEST_F(TriggerTest, RValueTrigger) {
-  auto& scheduler = CommandScheduler::GetInstance();
-  int counter = 0;
-  bool pressed = false;
-
-  RunCommand command([&counter] { counter++; }, {});
-
-  Trigger([&pressed] { return pressed; }).WhenActive(std::move(command));
-  scheduler.Run();
-  EXPECT_EQ(counter, 0);
-  pressed = true;
-  scheduler.Run();
-  EXPECT_EQ(counter, 1);
-}
-WPI_UNIGNORE_DEPRECATED
-
 TEST_F(TriggerTest, Debounce) {
   auto& scheduler = CommandScheduler::GetInstance();
   bool pressed = false;