fix(messages): accept cache_control on Messages.parse

[Alphaxiaoteng]

Summary

• Fixes Messages.parse (and AsyncMessages.parse) don't take cache_control? #1907: Messages.parse / AsyncMessages.parse omitted cache_control even though Messages.create, Messages.stream, and beta.messages.parse already accept it.
• Forward the parameter into the /v1/messages body (same as create).
• Add sync/async regression tests that assert the request body includes cache_control.

Test plan

• uv run pytest tests/api_resources/test_messages_parse_cache_control.py -q → 2 passed
• Confirmed cache_control is present on both sync and async parse signatures

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