Society v2 (#11324)

* New Society

* More logic drafting

* More work

* Building

* Some tests

* Fixes

* Improvements to the voting process

* More tests

* Test number 20

* Tests

* 30 tests

* Another test]

* All tests enabled

* Minor stuff

* generate_storage_alias: Rewrite as proc macro attribute

This rewrites the `generate_storage_alias!` declarative macro as proc-macro attribute. While doing
this the name is changed to `storage_alias`. The prefix can now also be the name of a pallet. This
makes storage aliases work in migrations for all kind of chains and not just for the ones that use
predefined prefixes.

* Maintenance operations don't pay fee

* Fix compilation and FMT

* Moare fixes

* Migrations

* Fix tests and add migration testing

* Introduce lazy-cleanup and avoid unbounded prefix removal

* Fixes

* Fixes

* [WIP][Society] Adding benchmarking to the v2. (#11776)

* [Society] Adding benchmarking to the v2.

* [Society] Code review.

* [Society] Better code.

* Using clear() + clear_prefix() and adding more tests.

* Benchmarking again...

* Fix Cargo

* Fixes

* Fixes

* Spelling

* Fix benchmarks

* Another fix

* Remove println

---------

Co-authored-by: Bastian Köcher <info@kchr.de>
Co-authored-by: Artur Gontijo <arturgontijo@users.noreply.github.com>

substrate/frame/support/src/storage/mod.rs

@@ -202,6 +202,18 @@ pub trait StorageMap<K: FullEncode, V: FullCodec> {
 		f: F,
 	) -> Result<R, E>;
 
+	/// Mutate the value under a key if the value already exists. Do nothing and return the default
+	/// value if not.
+	fn mutate_extant<KeyArg: EncodeLike<K>, R: Default, F: FnOnce(&mut V) -> R>(
+		key: KeyArg,
+		f: F,
+	) -> R {
+		Self::mutate_exists(key, |maybe_v| match maybe_v {
+			Some(ref mut value) => f(value),
+			None => R::default(),
+		})
+	}
+
 	/// Mutate the value under a key.
 	///
 	/// Deletes the item if mutated to a `None`.