Decreasing memory footprint of Tech Mapping

[mjgleason]

❗ DO NOT MERGE ❗

This PR decreases the memory footprint of Tech Mapping to enable creation of tech maps for exclusions at 30m resolution. It does so primarily by writing the results in slices to the h5 dataset, rather than building it up as an array in memory and then writing the full array to disk. There are a few other memory-saving changes as well.

The PR also introduces a new CLI command tech-mapping which allows running the creation of tech maps in isolation from running supply curve aggregation.

This PR is technically breaking since the TechMapping.run() method used to return the tech map array. This functionality did not appear to be used anywhere (in the codebase or the tests), so I removed it since it more or less defeats the purpose of trying to optimize memory.

Note that this is built on #503 so I have (temporarily) pointed it to the mg/agg_zones branch for comparison.

TODOS:

• expose batch_size as parameter up the call chain

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 91.20000% with 11 lines in your changes missing coverage. Please review.

Project coverage is 87.71%. Comparing base (381a7b9) to head (ed50e6c).

Files with missing lines	Patch %	Lines
reV/supply_curve/cli_tech_mapping.py	74.07%	7 Missing ⚠️
tests/test_supply_curve_tech_mapping.py	89.74%	4 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff                @@
##           mg/agg_zones     #504      +/-   ##
================================================
- Coverage         87.72%   87.71%   -0.02%     
================================================
  Files               122      123       +1     
  Lines             18379    18445      +66     
================================================
+ Hits              16123    16179      +56     
- Misses             2256     2266      +10     

Flag	Coverage Δ
unittests	87.71% <91.20%> (-0.02%)	⬇️

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