Update production dockerfile build with static asset compilation

[blarghmatey]

Pre-Flight checklist

• [ ] Screenshots and design review for any changes that affect layout or styling
  • [ ] Desktop screenshots
  • [ ] Mobile width screenshots
• [ ] Migrations
  • [ ] Migration is backwards-compatible with current production code
• [ ] Testing
  • [ ] Code is tested
  • [x] Changes have been manually tested
• [ ] Settings
  • [ ] New settings are documented and present in app.json
  • [x] New settings have reasonable development defaults, if applicable

What are the relevant tickets?

https://github.com/mitodl/ol-infrastructure/issues/1249

What's this PR do?

• Add a separate build stage for installing and compiling JS dependencies and assets
• Add a toggle to disable mandatory settings for being able to run collectstatic during image build

How should this be manually tested?

Run the dockerfile build and ensure that static assets are compiled and collected in the final image

Where should the reviewer start?

Dockerfile

Any background context you want to provide?

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Screenshots (if appropriate)

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What GIF best describes this PR or how it makes you feel?

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[codecov-commenter]

Codecov Report

Merging #1025 (7a16d73) into master (8de7b30) will increase coverage by 0.00%. The diff coverage is 50.00%.

@@           Coverage Diff           @@
##           master    #1025   +/-   ##
=======================================
  Coverage   95.98%   95.99%           
=======================================
  Files         182      182           
  Lines        7356     7357    +1     
  Branches      254      254           
=======================================
+ Hits         7061     7062    +1     
  Misses        261      261           
  Partials       34       34           

Impacted Files	Coverage Δ
ui/apps.py	73.33% <0.00%> (ø)
odl_video/settings.py	87.91% <100.00%> (+0.06%)	:arrow_up:

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