* Companion for Trim compact solution for length during preparation

https://github.com/paritytech/substrate/pull/8317

* eliminate potential for overflow in OffchainSolutionLengthLimit

* Apply suggestions from code review

Co-authored-by: Guillaume Thiolliere <[email protected]>

* update substrate: cargo update -p sp-io

Co-authored-by: Kian Paimani <[email protected]>
Co-authored-by: Guillaume Thiolliere <[email protected]>