chore: limit code coverage report to files in src; omit generated files

[ashtonG]

Description

This PR updates the code reports generated by the frontend unit tests to only report code in the src folder, and omits vendor code and generated code from the reports. This is so the codecoverage report will be more accurate to what we actually care about.

Test Plan

no testing needed

Checklist

• Changes have been manually QA'd
• User-facing API changes need the "User-facing API Change" label.
• Release notes should be added as a separate file under docs/release-notes/.
  See Release Note for details.
• Licenses should be included for new code which was copied and/or modified from any external code.

Ticket

[netlify]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 41.43%. Comparing base (115bf13) to head (2ab6790).
Report is 12 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9003      +/-   ##
==========================================
- Coverage   47.49%   41.43%   -6.07%     
==========================================
  Files        1168      839     -329     
  Lines      176302   103481   -72821     
  Branches     2350     2337      -13     
==========================================
- Hits        83729    42873   -40856     
+ Misses      92415    60455   -31960     
+ Partials      158      153       -5     

Flag	Coverage Δ
harness	?
web	40.65% <ø> (-2.19%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

see 329 files with indirect coverage changes

[keita-determined]

LGTM
worked well locally