selftests/bpf: Add uprobe multi consumers test

Adding test that attaches/detaches multiple consumers on
single uprobe and verifies all were hit as expected.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240722202758.3889061-3-jolsa@kernel.org