Safe and sane multi-item storage removal (#11490)

* Fix overlay prefix removal result

* Second part of the overlay prefix removal fix.

* Report only items deleted from storage in clear_prefix

* Fix kill_prefix

* Formatting

* Remove unused code

* Fixes

* Fixes

* Introduce clear_prefix host function v3

* Formatting

* Use v2 for now

* Fixes

* Formatting

* Docs

* Child prefix removal should also hide v3 for now

* Fixes

* Fixes

* Formatting

* Fixes

* apply_to_keys_whle takes start_at

* apply_to_keys_whle takes start_at

* apply_to_keys_whle takes start_at

* Cursor API; force limits

* Use unsafe deprecated functions

* Formatting

* Fixes

* Grumbles

* Fixes

* Docs

* Some nitpicks 🙈

* Update primitives/externalities/src/lib.rs

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* Formatting

* Fixes

* cargo fmt

* Fixes

* Update primitives/io/src/lib.rs

Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>

* Formatting

* Fixes

Co-authored-by: Bastian Köcher <info@kchr.de>
Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>
Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>

substrate/frame/society/src/lib.rs

@@ -1067,6 +1067,7 @@ pub mod pallet {
 			Founder::<T, I>::kill();
 			Rules::<T, I>::kill();
 			Candidates::<T, I>::kill();
+			#[allow(deprecated)]
 			SuspendedCandidates::<T, I>::remove_all(None);
 			Self::deposit_event(Event::<T, I>::Unfounded { founder });
 			Ok(())
@@ -1511,6 +1512,7 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 				.collect::<Vec<_>>();
 
 			// Clean up all votes.
+			#[allow(deprecated)]
 			<Votes<T, I>>::remove_all(None);
 
 			// Reward one of the voters who voted the right way.
@@ -1695,6 +1697,7 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 				}
 
 				// Clean up all votes.
+				#[allow(deprecated)]
 				<DefenderVotes<T, I>>::remove_all(None);
 			}