selftests/bpf: Add kprobe session cookie test

Adding kprobe session test that verifies the cookie value
get properly propagated from entry to return program.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240430112830.1184228-8-jolsa@kernel.org