Filter template by regions or sub regions

[nick-gorman]

• Adds functionality to allow a template to be created with a subset of nem regions or subregions.
• Still need to add filtering for new_entrant_wind_and_solar_connection_costs, but waiting to see if the generator capacity expansion functionality will have updates that make this easier.

[codecov]

Codecov Report

❌ Patch coverage is 96.22642% with 6 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/ispypsa/templater/create_template.py	20.00%	2 Missing and 2 partials ⚠️
src/ispypsa/templater/filter_template.py	98.63%	0 Missing and 2 partials ⚠️

Files with missing lines	Coverage Δ
src/ispypsa/config/validators.py	93.61% <100.00%> (+0.51%)	⬆️
src/ispypsa/templater/__init__.py	100.00% <100.00%> (ø)
src/ispypsa/templater/filter_template.py	98.63% <98.63%> (ø)
src/ispypsa/templater/create_template.py	86.95% <20.00%> (-8.17%)	⬇️

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