Adding uprobe_multi test for skeleton load/attach functions,
to test skeleton auto attach for uprobe_multi link.

Test that bpf_get_func_ip works properly for uprobe_multi
attachment.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20230809083440.3209381-20-jolsa@kernel.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>