Add Debouncer (#3590)

Supersedes #2358 with updates and cleanups.

Closes #2482 and closes #2487 because we shouldn't support both
time-based and count-based debouncing approaches.

Co-authored-by: oblarg <emichaelbarnett@gmail.com>

wpilibNewCommands/src/main/native/include/frc2/command/button/Trigger.h

@@ -9,6 +9,7 @@
 #include <memory>
 #include <utility>
 
+#include <units/time.h>
 #include <wpi/span.h>
 
 #include "frc2/command/Command.h"
@@ -345,6 +346,15 @@ class Trigger {
     return Trigger([*this] { return !m_isActive(); });
   }
 
+  /**
+   * Creates a new debounced trigger from this trigger - it will become active
+   * when this trigger has been active for longer than the specified period.
+   *
+   * @param debounceTime the debounce period
+   * @return the debounced trigger
+   */
+  Trigger Debounce(units::second_t debounceTime);
+
  private:
   std::function<bool()> m_isActive;
 };