Pass OwnedRpcParams to async methods (#410)

* Pass OwnedRpcParams to async methods

* Cow-ified RpcParams

* fmt

* Separate `RpcParamsSequence` parser from `RpcParams`

* Remove OwnedId, use Id<'static> instead

* Ensure that parsed `Id` is borrowing from input slice

* Tweak/add some docs
Test that parse() works after calling sequence()

* Fix rustdoc link

Co-authored-by: Maciej Hirsz <[email protected]>