RFR 15 8243099: SO_INCOMING_NAPI_ID support

[Alan Bateman]

Vladimir,

I think we should create some documentation for this socket option.

In JDK-8243099 you mention tests done with Apache Kafka so I assume that 
somebody has already modified Kafka to use this feature and maybe it 
would useful to document what was done and use that as a basis for 
something that we can turn into documentation. The context for asking is 
somebody showing up on net-dev in 2025 and asking for examples or more 
information on how to use this support option. Unlikely other socket 
options, this one may require significant changes to a framework or 
application, maybe when it selects the thread when dispatching a socket 
ready for I/O.

I think we should also include some of the commands used in any 
configuration. It doesn't need to be exhaustive but just listing one or 
two examples will help when somebody shows up with questions on how to 
use it.

I'm not sure yet where the best place to publish this documentation is 
(maybe the group/net area) but we can at least link to it from the 
release note that we'll need to create.

-Alan