Support more tcp socket option

[escoffier]

TcpSocketOptions can set IPV6_V6ONLY only right now. In our use case, we would like to set IP_TRANSPARENT flag. Some other users may have needs to set socket options toos.

pingora/pingora-core/src/listeners/l4.rs

Lines 54 to 61 in 0de54eb

	#[derive(Clone, Debug)]
	pub struct TcpSocketOptions {
	/// IPV6_V6ONLY flag (if true, limit socket to IPv6 communication only).
	/// This is mostly useful when binding to `[::]`, which on most Unix distributions
	/// will bind to both IPv4 and IPv6 addresses by default.
	pub ipv6_only: bool,
	// TODO: allow configuring reuseaddr, backlog, etc. from here?
	}

Describe the solution you'd like

provide more flag for TcpSocketOptions