selftests/bpf: Add stacktrace ips test for uprobe/uretprobe

Adding test that attaches uprobe/uretprobe verifies the
kernel part of the stacktrace is empty.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20260126211837.472802-6-jolsa@kernel.org