Update appropriate configuration properties to use the `Duration`
type, rather than an ad-hoc mix of milliseconds or seconds.

Configuration properties can now be defined in a consistent and readable
way. For example `server.session.timeout=5m`.

Properties that were previously declared using seconds are annotated
with `@DurationUnit` to ensure a smooth upgrade experience. For example
`server.session.timeout=20` continues to mean 20 seconds.

Fixes gh-11080