fix(retry): forward informational responses

[mcollina]

Forward 1xx informational responses through RetryHandler without recording them as final response state. Adds coverage for a 103 Early Hints response followed by a successful response.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.51%. Comparing base (f59b0f2) to head (ef3e1c8).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5625   +/-   ##
=======================================
  Coverage   93.50%   93.51%           
=======================================
  Files         110      110           
  Lines       38436    38441    +5     
=======================================
+ Hits        35940    35947    +7     
+ Misses       2496     2494    -2     

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