Improve updating expected bundle size

[melitele]

The intent of this PR is to make it easier to manipulate the expected bundle size. Instead of hardcoding the value of expected bundle size in the test file it puts in in a JSON file.

It also introduces one method of updating the expected bundle size automatically by running a build test with the parameter UPDATE set to true:

UPDATE=true npm run test-build -- min.test.ts

Launch Checklist

• Confirm your changes do not include backports from Mapbox projects (unless with compliant license) - if you are not sure about this, please ask!
• Briefly describe the changes in this PR.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.41%. Comparing base (53df3ad) to head (6014bc2).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6823   +/-   ##
=======================================
  Coverage   92.41%   92.41%           
=======================================
  Files         288      288           
  Lines       23807    23807           
  Branches     5055     5055           
=======================================
  Hits        22002    22002           
  Misses       1805     1805           

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[HarelM]

THANKS!!