Cleanup fs2-io networking support

[mpilquist]

This PR cleans up a bunch of things in the fs2-io networking support. Some of these are API annoyances and others are performance enhancements. Goal is to be competitive with fs2-netty when using nio backend, though not epoll or io_uring backends.

Use ip4s

This is something that's bothered me for a very long time. Before this PR, we used java.net.{InetAddress, InetSocketAddress} in these APIs. These are pretty dangerous, as simple looking expressions end up with side effects and blocking. For example: new InetSocketAddress("google.com", 443) does a DNS lookup and since it's not wrapped by F.blocking, it blocks a thread on compute pool.

In this PR, we use the types from https://github.com/comcast/ip4s, which are all immutable and safe. DNS resolution is handled via .resolve[F] on Host.

Since APIs change here, I'd appreciate comments on the approach even if you don't have the time or desire to do a whole review. :)

Manage SocketOptions Better

The various socket constructors took a bunch of standard socket options as params and defaulted them to adhoc values (e.g. .open(receiveBufferSize = 256 * 1024)). This PR gets rid of all of those defaulted parameters and instead takes a single List[SocketOption] where SocketOption is defined in fs2 and contains a constructor for each standard socket option as well as the ability to construct custom socket options. We'll get better defaults this way, as the JDK / OS will pick the unspecified values.

Package Layout and Renames

This PR introduces a new fs2.io.net package which contains both TCP and UDP support. The fs2.io.tls package is now fs2.io.net.tls.

The UDP types were renamed: Packet is now Datagram, Socket is now DatagramSocket, and SocketGroup is now DatagramSocketGroup.

Remove Socket Timeouts

This PR also removes the optional timeout parameter from socket read/writes in favor of using effect timeouts. E.g., socket.read.timeout(1.minute). These were mostly holdovers from when effect types didn't support timeouts.

Make SocketGroups Optional

Like Java NIO, we now have an internal set of global socket groups. We retain the ability to allocate explicit socket groups but 99.9% of applications should be able to use the global socket groups.

Simplify TCP Server Signatures

The server and serverResource methods on SocketGroup were unnecessarily complex. They've been simplified to take advantage of FS2 resource scoping rules. The server operation now returns a Stream[F, Socket[F]] instead of a Stream[F, Resource[F, Socket]]. A similar simplification was made to serverResource.

Remove Socket#close

The Socket#close method was removed, as socket lifecycle is managed by the Resource it is created in.

[SystemFw]

Assuming the library is decently documented, and it passed your bar for stability, I'm all for not having to mess around with weird java types. I think the introduction of scodec-bits, for example, payed nice dividends, and I think the same applies here :)

[mpilquist]

Assuming the library is decently documented

I wrote it, though that might work against me on the "decently documented" front. :) Though I think this one is documented pretty well.

[matthughes]

why did timeout get removed here?

[matthughes]

nevermind i see your comment now.