bpf: Add cookie support to programs attached with kprobe multi link

Adding support to call bpf_get_attach_cookie helper from
kprobe programs attached with kprobe multi link.

The cookie is provided by array of u64 values, where each
value is paired with provided function address or symbol
with the same array index.

When cookie array is provided it's sorted together with
addresses (check bpf_kprobe_multi_cookie_swap). This way
we can find cookie based on the address in
bpf_get_attach_cookie helper.

Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220316122419.933957-7-jolsa@kernel.org

tools/include/uapi/linux/bpf.h

@@ -1487,6 +1487,7 @@ union bpf_attr {
 				__u32		cnt;
 				__aligned_u64	syms;
 				__aligned_u64	addrs;
+				__aligned_u64	cookies;
 			} kprobe_multi;
 		};
 	} link_create;