selftests/net: packetdrill: import tcp/ecn, tcp/close, tcp/sack, tcp/tcp_info

selftests/net: packetdrill: import tcp/ecn, tcp/close, tcp/sack, tcp/tcp_info

Same as initial tests, import verbatim from
github.com/google/packetdrill, aside from:

- update `source ./defaults.sh` path to adjust for flat dir
- add SPDX headers
- remove author statements if any
- drop blank lines at EOF

Same test process as previous tests. Both with and without debug mode.
Recording the steps once:

make mrproper
vng --build \
--config tools/testing/selftests/net/packetdrill/config \
--config kernel/configs/debug.config
vng -v --run . --user root --cpus 4 -- \
make -C tools/testing/selftests TARGETS=net/packetdrill run_tests

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Soham Chakradeo <sohamch@google.com>
Link: https://patch.msgid.link/20241217185203.297935-2-sohamch.kernel@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>