Release v0.50.0

Changed

• The upstream.Options.QUICTracer field now has a type of upstream.QUICTraceFunc.

Removed

• Previously deprecated proxyutil functions UDPGetOOBSize, UDPSetOptions, UDPRead, UDPWrite, ContainsIP, AppendIPAddrs, SortIPAddrs, DNSSize, ReadPrefixed, WritePrefixed, and the error ErrTooLarge.