3cfd746bbc Add functionality to serialize signatures to a writer (Tobin C. Harding)
Pull request description:
Serializing the ecdsa and taproot `Signature` straight to a writer is a useful thing to be able to do.
Add `to_writer` to both `SerializedSignature`s and also to the `Signature`s (calling through to `SerializedSignature`).
Remove TODO comments from code.
ACKs for top commit:
Kixunil:
ACK 3cfd746bbc
Tree-SHA512: 82eb6d42c7b327cdfe5e89348890e45ea39c664420f7ea17d7826a5c388c7aaae917b1334e3f3df645fc4a81a11b59d97c7d6958e99077fbd67193e2a588f2eb