selftests/bpf: add raw_tp/tp_btf BPF cookie subtests

Add test validating BPF cookie can be passed during raw_tp/tp_btf
attachment and can be retried at runtime with bpf_get_attach_cookie()
helper.

Acked-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Message-ID: <20240319233852.1977493-6-andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>