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)
Done as part of flattening the `util` module.
We have a function in `util::misc` that operates on scripts, it is an
implementation of `FindAndDelete` from Bitcoin Core and is primarily
useful for supporting `CODESEPARATOR`, which we do not support.
Move the public `script_find_and_remove` function out of `util/misc.rs` and into
`util/mod.rs`, delete the testing and deprecate the function.