`Signature` only supported serialization into `Vec` which required a
heap allocation as well as prevented statically proving maximum length.
Adding a specialized type that holds a byte array and size solves this.
The solution is very similar to `secp256k1::ecdsa::SerializedSignature`.
The difference is that serialized signature in this crate contains
sighash bytes flag while in `secp256k1` it doesn't.
We use `internals::hex::display::DisplayHex` in many places, we can
improve ergonomics of the `internals` crate by re-exporting it from the
`prelude` module.
The `ToHex` trait was replaced by either simple `Display`/`LowerHex`
where appropriate or `DisplayHex` from `bitcoin_internals` which is
faster.
This change replaces the usages and removes the trait.
Done as part of flattening util.
Currently in `util` module we have a bunch of modules that provide
cryptography related functionality.
Create a `crypto` module and move into it the following:
- ecdsa
- schnorr
- key
To improve uniformity and ergonomics, do the following re-names while we
are at it:
- EcdsaSig -> ecdsa::Signature
- SchnorrSig -> schnorr::Signature
- EcdsaSigError -> ecdsa::Error
- SchnorrSigError -> schnorr::Error
- InvalidSchnorrSigSize -> InvalidSignatureSize (this is an error enum variant)