IO::Socket::IP non-blocking connect works a bit differently than
IO::Socket::INET6. Tweak the non-blocking for connect in the
sosplice scapy test.

Replace deprecated IO::Socket::INET6 with IO::Socket::IP.

Test more variations of TCP packets in the scapy splicing tests.
Delay connect and SYN+ACK to splice data into a connecting socket.

Reengineer the socket splicing regression tests:
- Move the tests from splice to new sosplice directory for consistent naming.
- Split the API tests and the TCP splicing tests into separate directori

Reengineer the socket splicing regression tests:
- Move the tests from splice to new sosplice directory for consistent naming.
- Split the API tests and the TCP splicing tests into separate directories.
- Create some tests for the upcoming UDP splicing.
- Tests can be run in obj directories now.
- The API tests can run both on a local and on a remote machine now.
- Fix the forking TCP tests which splice and read or write simultaneously.
- Bunch of little fixes for races in the tests.
- Deduplicate code, move checks into common functions.

show more ...