Fuzzer for Pallet Bags List (#9851)

* Fuzzer for Pallet Bags List

* Some small updates

* Fuzzer for Pallet Bags List

This PR adds a fuzzer for the `SortedListProvider` API exposed by pallet-bags-list.

* Feature gate code NOT used by fuzz feature

* Create Enum for list actions

* fix some small mistakes

* try and make CI happy

* fmt

* Do not insert before updating

* clean up some misc. comments

* marginally improve Node::sanity_check

* Change ID_RANGE to 25_000

* comma

* try improve correct feature gating so no unused code

Co-authored-by: thiolliere <[email protected]>