- Improve the performance of both the online and whole-file backup validation
methods.
- Add a CLI utility to "scramble" backups by removing the most obvious
identifying information.
- Import various backup validation proto changes, and tighten validation of
distribution lists to disallow duplicate entries.
- Java: the key transparency Store abstraction has been reworked.
- The version of our `boring` dependency is now v4.13.0, which incorporates the
changes of the upstream project through the same version.
