This renames `Script` to `ScriptBuf` and adds unsized `Script` modeled
after `PathBuf`/`Path`. The change cleans up the API a bit, especially
all functions that previously accepted `&Script` now accept truly
borrowed version. Some functions that perviously accepted `&[u8]` can
now accept `&Script` because constructing it is no loger costly.
We are trying to flatten the `util` module. The `taproot` module can
live in the crate root. If/when we create a `crypto` module/crate we may
wish to pull some stuff out of this module but for now moving it gets us
closer to removing `util` without making the directory structure any
worse.
Includes adding rustfmt attributes to skip formatting of macros.