bpf/selftests: Add selftest for bpf_smc_hs_ctrl

bpf/selftests: Add selftest for bpf_smc_hs_ctrl

This tests introduces a tiny smc_hs_ctrl for filtering SMC connections
based on IP pairs, and also adds a realistic topology model to verify it.

Also, we can only use SMC loopback under CI test, so an additional
configuration needs to be enabled.

Follow the steps below to run this test.

make -C tools/testing/selftests/bpf
cd tools/testing/selftests/bpf
sudo ./test_progs -t smc

Results shows:
Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: D. Wythe <alibuda@linux.alibaba.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Tested-by: Saket Kumar Bhaskar <skb99@linux.ibm.com>
Reviewed-by: Zhu Yanjun <yanjun.zhu@linux.dev>
Link: https://patch.msgid.link/20251107035632.115950-4-alibuda@linux.alibaba.com