This change enables preloading string arguments for USDT hooks. A
previous commit enabled this on the bpf side. This commit adds the
required logic for the user space side.

As USDT hooks apply to user space programs, some of the program's memory
may not be paged in when the hook fires. Adding this sleep-able program
allows us to handle this scenario by triggering page faults as required
to facilitate argument reading.

Signed-off-by: Andy Strohman <astrohma@isovalent.com>