Improve WWatch3 wind and currents forcing file generation

[douglatornell]

These changes were motivated by the intermittent stalls of the make_ww3_current_file and make_ww3_wind_file workers that have plagued operations for the past year. The changes reflect the many things that have been learned about using xarray.opern_dataset(), xarray.open_mfdataset(), and dask since the workers were written.

• Change to h5netcdf package for dataset reads in the hop of improving the reliability of the make_ww3_current_file and make_ww3_wind_file workers
• Remove more unnecessary variables for dataset reads to reduce the memory load
• Adjust time_counter chunk sizes based on testing to improve performance
• Change to use processes instead of the default threads for dask processing and explicitly call the .compute() before writing the datasets to force read processing with h5netcdf in the process-based dask scheduler
• Explicitly use netcdf4 as the engine for dataset writing. This avoids incompatibilities in the resulting file that arise if it is written using h5netcdf
• improve worker main() function docstrings re: issue #121

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 77.64%. Comparing base (1eca15e) to head (6cda311).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #271 +/- ## ========================================== + Coverage 77.63% 77.64% +0.01% ========================================== Files 133 133 Lines 18686 18695 +9 Branches 1910 1910 ========================================== + Hits 14506 14515 +9 Misses 4113 4113 Partials 67 67 ``` | [Flag](https://app.codecov.io/gh/SalishSeaCast/SalishSeaNowcast/pull/271/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=SalishSeaCast) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/SalishSeaCast/SalishSeaNowcast/pull/271/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=SalishSeaCast) | `77.64% <100.00%> (+0.01%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=SalishSeaCast#carryforward-flags-in-the-pull-request-comment) to find out more.

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[douglatornell]

Successfully tested in production on arbutus since 1-Jun-2024. No worker stalls, but we sometimes went 30 days without a stall with the previous code. Merging because this PR doesn't break anything, and there is reason to hope that it improves the reliability of the workers.