The API to compute the duration between instants can be hard to find and not straight-forward.

A new method on Instant to return the duration `until` another Instant is suggested.

Discussion on core-libs-dev:
https://mail.openjdk.org/pipermail/core-libs-dev/2024-April/122131.html
https://mail.openjdk.org/pipermail/core-libs-dev/2024-April/122137.html