Add UK Parliamentary constituency estimates

[nikhilwoodruff]

Fixes #2191

[anth-volk]

Hey @nikhilwoodruff, thanks for all of this. TL;DR:

1. I believe Northern Irish and Welsh runs would crash with these changes
2. I've flagged a few places I think typing and/or Pydantic schematization/dataclasses would be beneficial
3. I think we should really discuss codifying "primary," "secondary," and "tertiary" country-level entities throughout the system, as I think this code illustrates the limits of the single-tier "region" designation

[anth-volk]

Per discussions with Nikhil, we'll be handling the sub-national entity standardization question in a separate issue down the road, which I'll be opening as an issue in -core.

[codecov]

Codecov Report

Attention: Patch coverage is 31.16883% with 53 lines in your changes missing coverage. Please review.

Project coverage is 74.49%. Comparing base (b201ce4) to head (6056330).
Report is 18 commits behind head on master.

Files with missing lines	Patch %	Lines
policyengine_api/endpoints/economy/compare.py	32.55%	29 Missing ⚠️
...ngine_api/jobs/calculate_economy_simulation_job.py	14.28%	24 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2195      +/-   ##
==========================================
- Coverage   75.48%   74.49%   -0.99%     
==========================================
  Files          78       78              
  Lines        2921     2992      +71     
  Branches      309      322      +13     
==========================================
+ Hits         2205     2229      +24     
- Misses        651      698      +47     
  Partials       65       65              

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[anth-volk]

Thanks @nikhilwoodruff! I'll move onto the corresponding front-end PR now. Just had a question meant to double-check something, as well as a couple minor comments.