Deprecate `frame_system::Consumer`

[ggwpez]

frame_system::Consumer is obsolete / unused. Check the same for SelfSufficient, Provider and HandleLifetime:

polkadot-sdk/substrate/frame/system/src/lib.rs

Lines 2268 to 2278 in 63c73bf

	/// Event handler which registers a consumer when created.
	pub struct Consumer<T>(PhantomData<T>);
	impl<T: Config> HandleLifetime<T::AccountId> for Consumer<T> {
	fn created(t: &T::AccountId) -> Result<(), DispatchError> {
	Pallet::<T>::inc_consumers(t)
	}
	fn killed(t: &T::AccountId) -> Result<(), DispatchError> {
	Pallet::<T>::dec_consumers(t);
	Ok(())
	}
	}

Should be deprecated if no usage is found. Follow the deprecation checklist.

[tifecool]

Hey @ggwpez

Picking this up!

[tifecool]

@ggwpez added the deprecation notice for HandleLifetime.

Would like to see the CI run.