selftests/bpf: add global subprog annotation tests

Add test cases to validate semantics of global subprog argument
annotations:
  - non-null pointers;
  - context argument;
  - const dynptr passing;
  - packet pointers (data, metadata, end).

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20231215011334.2307144-10-andrii@kernel.org


Signed-off-by: Alexei Starovoitov <ast@kernel.org>