Merges upstream commits:
- bec321d Fix DPI detection: skip GREASE cipher suite in ClientHello parsing
- eb56493 Add separate handshake timeout
- 39ab557 Small refactoring
- 5bf218f Do not use default TLS cipher
Conflict resolution:
- Kept ReadClientHelloMulti for multi-secret support
- Preserved Secrets/Throttle/APIBindTo features from dolonet fork
- Removed per-connection SetReadDeadline from ReadClientHelloMulti
(superseded by proxy-level handshake timeout via SetDeadline)