bpf: Add support for tracing_multi link cookies

Add support to specify cookies for tracing_multi link.

Cookies are provided in array where each value is paired with provided
BTF ID value with the same array index.

Such cookie can be retrieved by bpf program with bpf_get_attach_cookie
helper call.

We need to sort cookies array together with ids array in check_dup_ids,
to keep the id->cookie relation.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20260606123955.345967-15-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

include/uapi/linux/bpf.h

@@ -1880,6 +1880,7 @@ union bpf_attr {
 			} cgroup;
 			struct {
 				__aligned_u64	ids;
+				__aligned_u64	cookies;
 				__u32		cnt;
 			} tracing_multi;
 		};