[WIP] Web server utilities

[esoteric-ephemera]

Second pass trying to integrate essential web server utilities with the client that will be used in web + MPShips

Keeping this open until local deployments in web seem performant

Major changes:

• MPRester itself performs checks on flask headers only as needed. If flask isn't installed, then MPRester functions as before
• is_localhost renamed to is_dev_env per internal discussion
• Removed session <-> worker assignment and migrated back to web

[codecov-commenter]

Codecov Report

❌ Patch coverage is 87.50000% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.80%. Comparing base (5994c58) to head (cd1718e).

Files with missing lines	Patch %	Lines
mp_api/client/_server_utils.py	76.47%	4 Missing ⚠️
mp_api/client/mprester.py	95.23%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1067      +/-   ##
==========================================
+ Coverage   85.68%   86.80%   +1.11%     
==========================================
  Files          47       47              
  Lines        2675     2682       +7     
==========================================
+ Hits         2292     2328      +36     
+ Misses        383      354      -29     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.