test: scale keepAliveTimeoutBuffer with platformTimeout

[geeksilva97]

Fixes #60656

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.66%. Comparing base (68d7b6f) to head (a1e999f).
⚠️ Report is 355 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #62364      +/-   ##
==========================================
- Coverage   89.77%   89.66%   -0.12%     
==========================================
  Files         673      676       +3     
  Lines      203820   206693    +2873     
  Branches    39175    39578     +403     
==========================================
+ Hits       182987   185332    +2345     
- Misses      13152    13494     +342     
- Partials     7681     7867     +186     

see 252 files with indirect coverage changes

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