cl/440413397: ghost: add cgroup_scraper.sh
cl/440413397: ghost: add cgroup_scraper.sh

Since we can add tasks to an enclave with ghostfs, we can use a shell script to
scrape the cgroups instead of an agent thread with custom C++ code (of which we
have *two* copies in prodkernel/ghost).

Tested: SLL and agent_biff

google/ghost-userspace,google/ghost-userspace,google/ghost-userspace,google/ghost-userspace