add stats for all Knob frame types
add stats for all Knob frame types

Summary:
Was not up to date. Most knobs would get categorized as `UNKNOWN`.

Adding comments for all the existing knobs.
If this causes an explosion in counters, perhaps we can remove the per-vip counter and just add one counter per type?

Reviewed By: mjoras

Differential Revision: D32274095

fbshipit-source-id: eb543683a101d4b2e7ba6218352027fb5149b354

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