Adding uprobe_multi test for bpf_link_create attach function.

Testing attachment using the struct bpf_link_create_opts.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20230809083440.3209381-22-jolsa@kernel.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>