Add new .wast tests to assert correct local.set result overwrites

[Robbepop]

This is in anticipation of #1512.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.23%. Comparing base (d73abed) to head (ec29648).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1561      +/-   ##
==========================================
- Coverage   72.24%   72.23%   -0.01%     
==========================================
  Files         179      179              
  Lines       16331    16331              
==========================================
- Hits        11798    11797       -1     
- Misses       4533     4534       +1     

☔ 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.