[chore] switch tests back to Bytes sizer

[mterhar]

Description

Some tests broke on Main a while ago and it looks like they changed from a sizer looking at bytes to items. This commit changes it back.

Testing

The items sizer test fails sometimes due to a timing situation that doesn't happen when looking at bytes.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.25%. Comparing base (f76ed03) to head (53ad03b).

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #14176   +/-   ##
=======================================
  Coverage   92.25%   92.25%           
=======================================
  Files         658      658           
  Lines       41186    41186           
=======================================
  Hits        37995    37995           
  Misses       2184     2184           
  Partials     1007     1007           

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