Reduce flakiness of wasm tests

[tstirrat15]

Fixes #449
Part of #575

Description

We made a similar change in the SpiceDB repo that seems to be helping. This brings it into the zed repo.

Changes

• Use depot runners
• Use cleanenv to make it work on the depot runner

Testing

Review. See that tests pass.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 41.72%. Comparing base (7ed5ab0) to head (06ebc62).
⚠️ Report is 14 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #576      +/-   ##
==========================================
+ Coverage   39.28%   41.72%   +2.44%     
==========================================
  Files          37       37              
  Lines        5448     4760     -688     
==========================================
- Hits         2140     1986     -154     
+ Misses       3063     2517     -546     
- Partials      245      257      +12     

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