Add new `descriptor` parameter that returns relays or bridges by digest of recently published descriptors

This suggestion is based on discussions with Sebastian related to #13135 (moved).

We should add a new parameter, let's call it descriptor, that returns relays or bridges by the digest of recently published descriptors. This includes all kinds of descriptors published by relays/bridges, so server descriptors and extra-info descriptors, and descriptors derived from those by the directory authorities, namely microdescriptors. We probably don't have to support partial digests, but we might want to support both hex-encoded and base64-encoded digests.

Example request (not working yet):

https://onionoo.torproject.org/details?descriptor=S+wzq/7JtC5fWkQmH3pxVprpdeWpGRLvrmKr6ZO/+3Y