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.
In preparation for emptying the `internal_macros` module move the
`serde_string_impl` and `serde_struct_human_string_imp` macros to the
`serde_utils` module.
Rationale: `internal_macros` stuff can go over in the `internals` crate
now that we have one. The serde macros could go over there but we have a
`serde_utils` module that holds code for implementing serde traits,
these two macros are exactly that.
Create a directory `bitcoin` and move into it the following as is with
no code changes:
- src
- Cargo.toml
- contrib
- test_data
- examples
Then do:
- Add a workspace to the repository root directory.
- Add the newly created `bitcoin` crate to the workspace.
- Exclude `fuzz` and `embedded` crates from the workspace.
- Add a contrib/test.sh script that runs contrib/test.sh in each
sub-crate
- Fix the bitcoin/contrib/test.sh script