intro misctrl

Generic binary for managing the /misc partition.

This CL only uses it to do a basic health check for the /misc
partition, but the idea is this is a single place that can manage
misc partition operations for the Android platform, rather than
having to write a new tool each time.

Bug: 317262681
Test: boot, check bugreport
Change-Id: I29a4189e2e9aee57cf66520207297d39d666f7a4