[DO NOT MERGE] Iain/web 3479 reduce yarn postinstall steps cache

[iainsproat]

Description & motivation

Experiments in CI to determine if #4793 improves ability to cache yarn install

Changes:

To-do before merge:

Screenshots:

Validation of changes:

Checklist:

• My pull request follows the guidelines in the Contributing guide?
• My pull request does not duplicate any other open Pull Requests for the same update/change?
• My commits are related to the pull request and do not amend unrelated code or documentation.
• My code follows a similar style to existing code.
• I have added appropriate tests.
• I have updated or added relevant documentation.

References

[linear]

WEB-3479 Reduce `yarn` postinstall steps

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 58.73%. Comparing base (3e9f871) to head (a0705cb).
Report is 3 commits behind head on main.

❗ There is a different number of reports uploaded between BASE (3e9f871) and HEAD (a0705cb). Click for more details.

HEAD has 3 uploads less than BASE

Flag	BASE (3e9f871)	HEAD (a0705cb)
	4	1

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #4795       +/-   ##
===========================================
- Coverage   70.44%   58.73%   -11.71%     
===========================================
  Files         583      109      -474     
  Lines       25145     3967    -21178     
  Branches     3757      488     -3269     
===========================================
- Hits        17713     2330    -15383     
+ Misses       6252     1610     -4642     
+ Partials     1180       27     -1153     

☔ 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.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[iainsproat]

Cache path does not exist > need to make directory where we have specified cacheFolder