Bug 1822876: Add H3 ECH Telemetry. r=kershaw,necko-reviewers
This patch adds telemetry which records when H3 connections succeed / fail
and what kind of ECH they used. Our H3 ECH tests are extended to test these
different modes and that the telemetry is recorded correctly.
Differential Revision:
https://phabricator.services.mozilla.com/D172813
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