Remove strict_encoding dependency

[dr-orlovsky]

Crates are subjected to be used as a part of wider bitcoin ecosystem and should not be limited to client-side-validation only. Thus, strict encoding implementation for crate-defined types should be done inside strict_encoding crate, like it is done for bitcoin, miniscript, secp256k1 and other non-client-side-validation projects.

[cryptoquick]

This isn't quite clear. Are you saying, the types like the ones in descriptors/src/descriptor.rs that derive StrictEncode and StrictDecode should be moved into a separate strict_encoding crate? Could conditional compilation and features be used instead?

[dr-orlovsky]

I think that we should wait with this change since I am not sure anymore that this is a good idea