Add a simple MappedFile to libbase and switch fastboot and libziparchive over.

This allows us to remove libziparchive's dependency on libutils.

Bug: http://b/79112958
Test: ran libbase and libziparchive tests, ran fastboot manually
Change-Id: I95c651976dad222863e5b8c37d4514b778f5dce7
13 files changed