Do not pass DexFile to ClassLinker::Lookup/ResolveType().

The DexFile can be easily retrieved from the DexCache,
so reduce the number of arguments that need to be passed.

Also refactor the code to avoid doing the DexCache lookup
twice and avoid unnecessary read barriers in the initial
DexCache lookup (also for Lookup/ResolveField()).

Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing
Change-Id: Idea9aa42b6a5bade947e93e330b1abdb9d11b2da