Update quanta to 0.9

[ljedrz]

This PR updates the quanta dependency to the current version; note that the use of Instant::as_unix_duration was removed, as the crate no longer supports it due to it having been buggy: metrics-rs/quanta#46.

[ljedrz]

Note: this crate needs to depend on a fork of quanta that provides a way to construct Instant values from a u64 in order for arithmetic operations to work properly. Some methods had to be removed, but duration_since was added in order to share more API with std::time::Instant.

[ljedrz]

I updated the PR as suggested by the owner of quanta.