selftests/ftrace: Add selftest for testing duplicate eprobes and kprobes

Add a selftest that makes sure that eprobes and kprobes can not be created
with the same group and name as existing events.

Link: https://lore.kernel.org/linux-kselftest/20210819152825.715290342@goodmis.org/
Link: https://lkml.kernel.org/r/20210820204742.653288346@goodmis.org

Cc: "Tzvetomir Stoyanov" <tz.stoyanov@gmail.com>
Cc: Tom Zanussi <zanussi@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: linux-kselftest@vger.kernel.org
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>