Write some scripts to generate per-country rendezvous plots

We have client rendezvous method poll stats for snowflake, both total counts and per-country counts. Our circumvention settings are now distributing snowflake bridges using all three available rendezvous methods: sqs in cn, ampcache in tm, and http in ir.

It would be helpful to be able to easily generate plots of poll counts by country and method to detect and respond to unexpected drops.