We have three integer wrapping types that can be created from hex
strings where the conversion from an integer is infallible:
- `absolute::LockTime`
- `Sequence`
- `CompactTarget`
We would like to improve our handling of the two prefix characters (eg
0x) by making it explicit.
- Modify the inherent `from_hex` method on each type to error if the
input string does not contain a prefix.
- Add an additional inherent method on each type `from_unprefixed_hex`
that errors if the input string does contain a prefix.
This patch does not touch the wrapper types that cannot be infallibly
constructed from an integer (i.e. absolute `Height` and `Time`).
b873a3cd44