fix(retry): forward rawHeaders writes through RetryController

[official-burak]

Fixes #5726

RetryController forwarded rawHeaders / rawTrailers as getters only. DecompressHandler assigns a filtered list onto controller.rawHeaders when it strips content-encoding, so the documented order compose([retry(), decompress()]) threw:

TypeError: Cannot set property rawHeaders of #<RetryController> which has only a getter

This adds setters that write through to the active connection controller (no-ops before a connection is attached, same as pause/resume).

Tests

• Before: test/retry-handler-controller-proxy.js failed with the getter-only TypeError; retry composed before decompress can rewrite rawHeaders failed.
• After: those tests pass, plus the full decompress interceptor file (28), retry-handler (47), and interceptors/retry (16).

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.49%. Comparing base (af02617) to head (ecb0aaf).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5727   +/-   ##
=======================================
  Coverage   93.49%   93.49%           
=======================================
  Files         110      110           
  Lines       39050    39061   +11     
=======================================
+ Hits        36510    36521   +11     
  Misses       2540     2540           

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[mcollina]

lgtm