Introduce scheduler and use it for the democracy dispatch queue (#5412)

* Initial draft of the logic

* Build and tests

* Make work with new initialize infratructure.

* Update frame/scheduler/src/lib.rs

Co-Authored-By: Marcio Diaz <marcio.diaz@gmail.com>

* Update frame/scheduler/src/lib.rs

Co-Authored-By: Marcio Diaz <marcio.diaz@gmail.com>

* Update frame/scheduler/src/lib.rs

Co-Authored-By: Marcio Diaz <marcio.diaz@gmail.com>

* Update frame/scheduler/src/lib.rs

Co-Authored-By: Marcio Diaz <marcio.diaz@gmail.com>

* Fix test

* Update frame/scheduler/src/lib.rs

Co-Authored-By: Marcio Diaz <marcio.diaz@gmail.com>

* Rejig interface to make it more useful for democracy.

* Try to get democraxy module to make use of scheduler.

* Make democracy use scheduler.

* Use actual max weight for enactent

* Remove TODO

* Fix runtime build

* Minor cleanup

* Fix scheduler.

* Fix benchmarks

* Fix

* Fix

* Fix

* More bench fixes

* Fix

* Fix.

* Add more bench constants.

* Fix cancel_queued bench.

* Fix test comment.

* Update frame/scheduler/src/lib.rs

Co-Authored-By: Marcio Diaz <marcio.diaz@gmail.com>

Co-authored-by: Marcio Diaz <marcio.diaz@gmail.com>

substrate/Cargo.lock

@@ -3512,6 +3512,7 @@ dependencies = [
  "pallet-offences",
  "pallet-randomness-collective-flip",
  "pallet-recovery",
+ "pallet-scheduler",
  "pallet-session",
  "pallet-session-benchmarking",
  "pallet-society",
@@ -4044,6 +4045,7 @@ dependencies = [
  "frame-system",
  "hex-literal",
  "pallet-balances",
+ "pallet-scheduler",
  "parity-scale-codec",
  "serde",
  "sp-core",
@@ -4077,6 +4079,7 @@ dependencies = [
  "frame-system",
  "hex-literal",
  "pallet-balances",
+ "pallet-scheduler",
  "parity-scale-codec",
  "serde",
  "sp-core",
@@ -4314,6 +4317,21 @@ dependencies = [
  "sp-std",
 ]
 
+[[package]]
+name = "pallet-scheduler"
+version = "2.0.0-alpha.5"
+dependencies = [
+ "frame-benchmarking",
+ "frame-support",
+ "frame-system",
+ "parity-scale-codec",
+ "serde",
+ "sp-core",
+ "sp-io",
+ "sp-runtime",
+ "sp-std",
+]
+
 [[package]]
 name = "pallet-scored-pool"
 version = "2.0.0-alpha.5"