[Security] Sanitize Cookie headers in debug logs

[gonzaloriestra]

WHY are these changes introduced?

Sensitive session data from Cookie and Set-Cookie headers can currently be leaked in debug logs when network request info is printed. This poses a security risk if logs are shared or stored insecurely.

WHAT is this pull request doing?

This PR adds 'cookie' to the list of keywords in sanitizedHeadersOutput. This ensures that any header containing "cookie" (case-insensitive) is redacted from the debug output.

How to test your changes?

Run any command that performs a network request with cookies and check the debug logs. The Cookie and Set-Cookie headers should no longer appear in the "With request headers:" section of the output.

Duplicate check

I ran git log --grep="Security" --oneline -n 200 and git log --grep="Jules" --oneline -n 200 as a fallback since gh was unavailable. I found no previous PRs addressing this specific header sanitization.
Closest PR considered:

• 3a92d0375 Merge pull request #7481 from Shopify/fix/theme-push-fresh-dynamic-source-defaults: Touched the same file for theme-related fixes, but did not address security sanitization of headers.

Checklist

• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've considered possible documentation changes
• I've considered analytics changes to measure impact

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PR created automatically by Jules for task 10005827685003157313 started by @gonzaloriestra

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