Done as part of the effort to flatten the `util` module.
The `sighash` module can stand alone in the crate root, it provides a
discreet set of functionality - the `SighashCache` and associated types.
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