selftests/bpf: Add more tests for check_max_stack_depth bug

Another test which now exercies the path of the verifier where it will
explore call chains rooted at the async callback. Without the prior
fixes, this program loads successfully, which is incorrect.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20230717161530.1238-4-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>