Remove caching of api/fields due to memcached size limit

[rfrenchseti]

• Fixes #1294
• Were any Django, import pipeline, or table_schema files modified? Y
  • If YES:
  • Database used (or new import): opus3_test_221201
  • FLAKE8 run on modified code: Y
  • All Django tests pass: Y
  • Code coverage run and still at 100%: Y
• Were any JavaScript or CSS files modified? N
  • If YES:
  • JSHINT run on all affected files: Y/NA
  • Tested on Chrome, Firefox, Safari, Edge, and iOS: Y/NA (Remember to test all browser sizes)
  • Tested for race conditions (with delayed API calls if applicable): Y/NA
• Was the documentation reviewed for necessary changes or additions? NA
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Description of changes:

memcached has a 1MB limit on cached data, which we now exceed when returning /api/fields.json with a full database (but not with a test database). Caching has been removed for this API call and the relevant tests have also been removed.

Known problems:

/api/fields is now slower...

[rfrenchseti]

This branch is now running on the production server and successfully solved the problem with the log analyzer crashing.