metrics-web should display onion service v3 stats

Hello there,

now that tpo/core/tor#23126 (closed) has been merged it's time to incorporate the results to the website.

Only a few relays support the stats (since they've only been on tor master) but still the extrapolation code of metrics-web should take care of that.

When it comes to the number of onion services, the logic is identical between v2 and v3 stats but in the Extrapolator we should be dividing by 24 instead of 12. That's because in v3 onions, each descriptor has 2 replicas and 4 uploads for each replica, so in total each descriptor get uploaded to 8 HSDirs. Furthermore, each onion service maintains two descriptors at any given time (so 16 uploads), and rotates one descriptor at around 00:00UTC (so another 8 uploads). This means that between the interval of 12:00UTC to 12:00UTC the HSDirs will be exposed to 24 uploads for each HS. This is precisely the reason we choose to collect stats from 12:00UTC to 12:00UTC, and this logic has not been documented somewhere yet but we should find a good place to document it.

When it comes to the number of v3 rend cells, the logic should be identical between v2 and v3 stats entirely.

The extra-info format of v3 stats can be found here: tpo/core/torspec@1337eb21

Finally as discussed here tpo/core/tor#23126 (comment 2708017) the v3 stats are strictly collected from 12:00UTC to 12:00UTC every day and they should be attributed to the day where the interval ends.

Let me know if you have any questions! Thanks!

Let me know if you have any questions!!!