Scheduler cleanup

[gavofyork]

Scheduler should remove any trailing None items in agendas as items get removed.

A migration should do this for preexisting items.

[dharjeezy]

@gavofyork i will like to pick this up.

So, are you saying the Agenda storage map should not store this

BoundedVec<Option<ScheduledOf<T>>, T::MaxScheduledPerBlock> anymore

but store this instead

BoundedVec<ScheduledOf<T>, T::MaxScheduledPerBlock>?

[ggwpez]

Done in #12989

[Polkadot-Forum]

This issue has been mentioned on Polkadot Forum. There might be relevant details there:

https://forum.polkadot.network/t/polkadot-release-analysis-v0-9-37/1736/1