Add query frequency to mega PADD

[yubiuser]

What does this PR aim to accomplish?:

Builds upon #494 and adds query frequency to mega PADD. Needs pi-hole/FTL#2806

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[yubiuser]

I'm not sure if this is the best placement, but I thought client names usually are shorter than ad domains...

[PromoFaux]

Maybe in the System section above memory usage? Not sure...

[yubiuser]

I don't think it fits there. It's not an information about the system but rather FTL