Add the '$arg*' meta fetch argument for function-entry probe events. This
will be expanded to the all arguments of the function and the tracepoint
using BTF function argument information.

e.g.
 #  echo 'p vfs_read $arg*' >> dynamic_events
 #  echo 'f vfs_write $arg*' >> dynamic_events
 #  echo 't sched_overutilized_tp $arg*' >> dynamic_events
 # cat dynamic_events
p:kprobes/p_vfs_read_0 vfs_read file=file buf=buf count=count pos=pos
f:fprobes/vfs_write__entry vfs_write file=file buf=buf count=count pos=pos
t:tracepoints/sched_overutilized_tp sched_overutilized_tp rd=rd overutilized=overutilized

Also, single '$arg[0-9]*' will be converted to the BTF function argument.

NOTE: This seems like a wildcard, but a fake one at this moment. This
is just for telling user that this can be expanded to several arguments.
And it is not like other $-vars, you can not use this $arg* as a part of
fetch args, e.g. specifying name "foo=$arg*" and using it in dereferences
"+0($arg*)" will lead a parse error.

Link: https://lore.kernel.org/all/168507475126.913472.18329684401466211816.stgit@mhiramat.roam.corp.google.com/Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>