[cli] Attempt to fix the "lambda-with-3-second-timeout" E2E test

[TooTallNate]

This test has been failing a lot recently, with the 2 second timeout case receiving a 504 status code. My theory is that the cold-start time is making the 3 second timeout be hit, even though the sleep time is for 2 seconds. So test the two paths serially instead, and test the 2 second timeout last. This way, we know that the lambda has is hot.

Example: https://github.com/vercel/vercel/runs/3296671662

[codecov]

Codecov Report

Merging #6579 (0d310be) into main (3616bdf) will increase coverage by 0.17%.
The diff coverage is n/a.

❗ Current head 0d310be differs from pull request most recent head ba0fb75. Consider uploading reports for the commit ba0fb75 to get more accurate results

@@            Coverage Diff             @@
##             main    #6579      +/-   ##
==========================================
+ Coverage   12.33%   12.50%   +0.17%     
==========================================
  Files         271      271              
  Lines        9788     9788              
  Branches     1627     1627              
==========================================
+ Hits         1207     1224      +17     
+ Misses       8483     8463      -20     
- Partials       98      101       +3     

Impacted Files	Coverage Δ
src/util/dev/server.ts	49.78% <0.00%> (+0.85%)	⬆️
src/util/dev/builder-cache.ts	71.71% <0.00%> (+7.23%)	⬆️

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