libbpf: Cross-join available_filter_functions and kallsyms for multi-kprobes

When using regular expression matching with "kprobe multi", it scans all
the functions under "/proc/kallsyms" that can be matched. However, not all
of them can be traced by kprobe.multi. If any one of the functions fails
to be traced, it will result in the failure of all functions. The best
approach is to filter out the functions that cannot be traced to ensure
proper tracking of the functions.

Closes: https://lore.kernel.org/oe-kbuild-all/202307030355.TdXOHklM-lkp@intel.com/
Reported-by: kernel test robot <lkp@intel.com>
Suggested-by: Jiri Olsa <jolsa@kernel.org>
Suggested-by: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Signed-off-by: Jackie Liu <liuyun01@kylinos.cn>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230705091209.3803873-1-liu.yun@linux.dev