* Serialize `BlindedElement` as `GenericArray`
* Don't hold input
* Remove allocations from `VerifiableClient::batch_finalize`
* Remove all allocation from serialization
* Remove required `alloc` support.
* Fix accidental usage of 1.57 API
* Let `VerifiableClient::batch_finalize` return a concrete type
* Simplify de-serialization
* Remove custom Serde implementation