Merge branch 'Retire test_sock.c'

Jordan Rife says:

====================
This patch series migrates test cases out of test_sock.c to
prog_tests-style tests. It moves all BPF_CGROUP_INET4_POST_BIND and
BPF_CGROUP_INET6_POST_BIND test cases into a new prog_test,
sock_post_bind.c, while reimplementing all LOAD_REJECT test cases as
verifier tests in progs/verifier_sock.c. Finally, it moves remaining
BPF_CGROUP_INET_SOCK_CREATE test coverage into prog_tests/sock_create.c
before retiring test_sock.c completely.

Changes
=======
v1->v2:
- Remove superfluous verbose bool from the top of sock_post_bind.c.
- Use ASSERT_OK_FD instead of ASSERT_GE to test cgroup_fd validity.
- Run sock_post_bind tests in their own namespace, "sock_post_bind".
====================

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>