This introduces a couple of new service side metrics:
* `hs_intro_rejected_intro_req_count`, which counts the number of introduction
requests rejected by the hidden service
* `hs_rdv_error_count`, which counts the number of rendezvous errors as seen by
the hidden service (this number includes the number of circuit establishment
failures, failed retries, end-to-end circuit setup failures)
Closes#40755. This partially addresses #40717.
Signed-off-by: Gabriela Moldovan <gabi@torproject.org>
