Add MPTP usage

fix(mptp): make inbound CID session registration atomic under single write lock

Refactor DNS client

Add a DNS selector

Skip invalid DNS server

Use aws-lc-rs

Fix build and test

Improve openssl backend ECH handling

Improve ring backend ECH handling

Support DoH

Support ECH config DNS lookup

Support setting environment variables in JSON config

Support ECH

Fix Apple builds

Fix tests