Release v0.45.0.

Another step toward #46.

Maintenance:
- Update module dependencies.
- handler: fix an outdated comment
- Remove the custom queue implementation. (#93)

Breaking changes:
- code: remove the code registration hooks (#91)
- server: remove the Run helper (#92)

Although these changes are breaking, I surveyed existing usage visible from the
search engine, and did not find anything likely to care.