Investigate using `EpochNanoseconds` and implement wherever possible

[nekevss]

In #116, the EpochNanoseconds new type was added. The introduction of EpochNanoseconds was fairly bare, as further mentioned in #115. We should look into using EpochNanoseconds more throughout the codebase where it makes sense according to the proposal.

[JohannesHelleve]

I would like to try this one!

[nekevss]

This is more or less complete, and no longer planned.

The general conclusion:

The TimeZoneProvider trait is be redesigned and move out of temporal_rs, so it will not have access to EpochNanoseconds. Furthermore, there are intermediate points in calculations where an EpochNanosecond could actually exceed the allowed range.