Introduce srml/scored-pool (#3381)

* Introduce srml/scored-pool

* Bump impl_version

* Apply suggestions from code review

Co-Authored-By: Bastian Köcher <bkchr@users.noreply.github.com>

* Remove unnecessary pub use

* Remove unnecessary import

* Adapt to InitializeMembers

* Bump impl_version

* Implement remarks (shortens code)

* Improve complexity of score()

Search and remove and search again for the
new spot and insert then => O(2LogN).

* Get rid of a clone()

* Reduce complexity of issue_candidacy()

* Add CandidateScored event + Improve comments

* Fix naming

* Use Lookup instead of AccountId as param

* Use set_members_sorted instead of computing diff

* Remove function which is only used during genesis

* Get rid of rev() by changing sort order of Pool

* Rename issue_candidacy to submit_candidacy

* Shorten code

* Remove find_in_pool() and have transactor submit index

* Remove unnecessary dependency

* Improve error messages

* Improve naming

* Improve comments

* Make code clearer wrt which receiver to invoke

* Adapt to new system trait

* Refactor to request CandidateDeposit only once

* Refactor to request Pool only once

* Improve structure and comments

substrate/Cargo.lock

@@ -3995,6 +3995,21 @@ dependencies = [
  "substrate-primitives 2.0.0",
 ]
 
+[[package]]
+name = "srml-scored-pool"
+version = "1.0.0"
+dependencies = [
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
+ "sr-io 2.0.0",
+ "sr-primitives 2.0.0",
+ "sr-std 2.0.0",
+ "srml-balances 2.0.0",
+ "srml-support 2.0.0",
+ "srml-system 2.0.0",
+ "substrate-primitives 2.0.0",
+]
+
 [[package]]
 name = "srml-session"
 version = "2.0.0"