[commands] Merge CommandBase into Command and SubsystemBase into Subsystem (#5392)

Moves all CommandBase functionality into Command and deprecates CommandBase for removal.
Moves all SubsystemBase functionality into Subsystem and deprecates SubsystemBase for removal.
Adds a function to CommandScheduler to remove all registered Subsystems.

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

@@ -12,57 +12,4 @@
 
 using namespace frc2;
 
-SubsystemBase::SubsystemBase() {
-  wpi::SendableRegistry::AddLW(this, GetTypeName(*this));
-  CommandScheduler::GetInstance().RegisterSubsystem({this});
-}
-
-void SubsystemBase::InitSendable(wpi::SendableBuilder& builder) {
-  builder.SetSmartDashboardType("Subsystem");
-  builder.AddBooleanProperty(
-      ".hasDefault", [this] { return GetDefaultCommand() != nullptr; },
-      nullptr);
-  builder.AddStringProperty(
-      ".default",
-      [this]() -> std::string {
-        auto command = GetDefaultCommand();
-        if (command == nullptr) {
-          return "none";
-        }
-        return command->GetName();
-      },
-      nullptr);
-  builder.AddBooleanProperty(
-      ".hasCommand", [this] { return GetCurrentCommand() != nullptr; },
-      nullptr);
-  builder.AddStringProperty(
-      ".command",
-      [this]() -> std::string {
-        auto command = GetCurrentCommand();
-        if (command == nullptr) {
-          return "none";
-        }
-        return command->GetName();
-      },
-      nullptr);
-}
-
-std::string SubsystemBase::GetName() const {
-  return wpi::SendableRegistry::GetName(this);
-}
-
-void SubsystemBase::SetName(std::string_view name) {
-  wpi::SendableRegistry::SetName(this, name);
-}
-
-std::string SubsystemBase::GetSubsystem() const {
-  return wpi::SendableRegistry::GetSubsystem(this);
-}
-
-void SubsystemBase::SetSubsystem(std::string_view name) {
-  wpi::SendableRegistry::SetSubsystem(this, name);
-}
-
-void SubsystemBase::AddChild(std::string name, wpi::Sendable* child) {
-  wpi::SendableRegistry::AddLW(child, GetSubsystem(), name);
-}
+SubsystemBase::SubsystemBase() {}