Make libdexfile build independent of runtime dir

Remove libdexfile's dependency on utils.cc and move utf.cc into
/dex.  Remove libdexfile's constituent sources from libart and
use libdexfile wherever libart is. Also remove some ART-specific
interfaces.  Libdexfile's tests remain to be converted, plus
moving the files to a new directory peer to runtime/.

Bug: 22322814
Test: make -j 50 test-art-host
Change-Id: Ifaf695216e4a0e43d3aa377984d933f7a2a243c2