Add new casper socket service

[tig_freebsdfoundation.org]

Summary

Casper service to provide a connected socket

• lets user initialize allowed destinations in cap_socket_init(). destinations are of type "socket_type:hostname:portnumber" eg. "tcp:www.google.com:80" Hostname is mandatory while socket type and port number have sentinel value to allow any. eg. "any:127.0.0.1:-1" allows any connection to localhost
• cap_socket_connect() attempts to connect to destination provided if it's allowed. From what I've been seeing the user should pass a full destination. eg. "tcp:www.google.com:80" passing "any" or "-1" might cause socket() or connect() to fail.

Test Plan

server.c1 KBDownload

client.c898 BDownload

currently tested using a simple client and server on localhost.

[tig_freebsdfoundation.org]

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