Document that streaming responses don't auto-decompress

[Krishna2004V]

Fixes #2155

Summary

• Documents that streaming responses (stream=True with Response.raw) don't automatically decompress gzipped content, and provides the workaround.

Changes

• Added note to docs/user/advanced.rst in "Body Content Workflow" section
• Updated FAQ "Encoded Data?" section in docs/community/faq.rst
• Included examples with JSON and XML parsing