user_events: Optimize writing events by only copying data once

Pass iterator through to probes to allow copying data directly to the
probe buffers instead of taking multiple copies. Enables eBPF user and
raw iterator types out to programs for no-copy scenarios.

Link: https://lkml.kernel.org/r/20220118204326.2169-6-beaub@linux.microsoft.com



Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Beau Belgrave <beaub@linux.microsoft.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>