[MNG-8533] [MNG-5729] Use monotonic time measurements

[gnodet]

JIRA issue: MNG-8533

This PR introduces a MonotonicClock in the Maven API.
It provides accurate duration computation, and relative date/time support, leveragingSystem.nanoTime().
The clock is UTC-based and provided Instant need to be zoned if needed for correct display.

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https://issues.apache.org/jira/browse/MNG-5729

[cstamas]

Is this for rc2 or 4.1?

[gnodet]

Is this for rc2 or 4.1?

I'm on the edge. The updated PR is more lightweight and does not define a new Temporal implementation, but simply reuses the well known Instant instead, but provides a Clock implementation which uses the monotonic system clock. This makes the code a lot simpler and safer.

[cstamas]

This PR looks quite non-invasive, so I'd just merge it, make it rc2