1b0988833a Remove `ToHex` (Martin Habovstiak)
Pull request description:
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.
ACKs for top commit:
tcharding:
ACK 1b0988833a
apoelstra:
ACK 1b0988833a
Tree-SHA512: a1b508e24ac247a0692c01b7cb1e7fa8f23fbfa3d6c3d5dfe669eec01f940a96c3f88508cb0b2e3529eebd9cb51e7d41435dbd5f4cbaf3bc14b9c7e7d790308b