lib/test_fprobe: add testcase for mixed fprobe

lib/test_fprobe: add testcase for mixed fprobe

Add the testcase for the fprobe, which will hook the same target with two
fprobe: entry, entry+exit. And the two fprobes will be registered with
different order.

fgraph and ftrace are both used for the fprobe, and this testcase is for
the mixed situation.

Link: https://lore.kernel.org/all/20251015083238.2374294-3-dongml2@chinatelecom.cn/
Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>