Add some test cases to confirm the tailcall hierarchy issue has been fixed.

On x64, the selftests result is:

cd tools/testing/selftests/bpf && ./test_progs -t tailcalls
327/18  tailcalls/tailcall_bpf2bpf_hierarchy_1:OK
327/19  tailcalls/tailcall_bpf2bpf_hierarchy_fentry:OK
327/20  tailcalls/tailcall_bpf2bpf_hierarchy_fexit:OK
327/21  tailcalls/tailcall_bpf2bpf_hierarchy_fentry_fexit:OK
327/22  tailcalls/tailcall_bpf2bpf_hierarchy_fentry_entry:OK
327/23  tailcalls/tailcall_bpf2bpf_hierarchy_2:OK
327/24  tailcalls/tailcall_bpf2bpf_hierarchy_3:OK
327     tailcalls:OK
Summary: 1/24 PASSED, 0 SKIPPED, 0 FAILED

On arm64, the selftests result is:

cd tools/testing/selftests/bpf && ./test_progs -t tailcalls
327/18  tailcalls/tailcall_bpf2bpf_hierarchy_1:OK
327/19  tailcalls/tailcall_bpf2bpf_hierarchy_fentry:OK
327/20  tailcalls/tailcall_bpf2bpf_hierarchy_fexit:OK
327/21  tailcalls/tailcall_bpf2bpf_hierarchy_fentry_fexit:OK
327/22  tailcalls/tailcall_bpf2bpf_hierarchy_fentry_entry:OK
327/23  tailcalls/tailcall_bpf2bpf_hierarchy_2:OK
327/24  tailcalls/tailcall_bpf2bpf_hierarchy_3:OK
327     tailcalls:OK
Summary: 1/24 PASSED, 0 SKIPPED, 0 FAILED
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Leon Hwang <hffilwlqm@gmail.com>
Link: https://lore.kernel.org/r/20240714123902.32305-4-hffilwlqm@gmail.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>