Review Mozilla 2005800: Add Disable AI section to gen ai settings

🔍 Bugzilla Audit

Bugzilla: https://bugzilla.mozilla.org/show_bug.cgi?id=2005800

Description

Adds some browser.ai.control.* preferences to disable "AI" features. We may be able to use this to hide AI-related preferences. I wonder how these work alongside our ml preferences from #44045 (closed).

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