Added metrics for the relay-side hidden service interactions

Adds 4 counters:

• tor_relay_est_intro_total
• tor_relay_est_intro_total
• tor_relay_rend1_total
• tor_relay_intro1_total

Each counter is incremented exactly once when it's respective cell is handled. The action label is used to differentiate the outcome of handling each cell.

Ran this for a bit to make sure it functioned how I intended.

Example of the INTRO1 rates by action for my relay:

Interestingly upwards of 50% of what I assume to be DoS traffic here is "mistargetted" - the relay doesn't actually have the requested auth key in it's circuitmap.

Another pattern I noticed from the data was a near perfect correlation of 2x onionskins per intro1 cell received by the relay: I would have thought it would be 1:1 rather than 2:1 but maybe I misunderstand how this part of the protocol works.