Clean up hasSystemFeature binder cache

Bug: 140788621

This is a non-functional clean-up.
1. Rename the classes and methods used by the binder cache so that
   everything public is based off of the binder name "hasSystemFeature".
2. Modified the hashCode() method to conform to the comments in cl/9965760
3. Moved hasSystemFeatureUnchached() logic into the cache recompute() method.
4. Made the cache static so that there is on per process.  The recompute()
   method uses the binder handle from ActivityThread, which is the same
   handle that is passed to all other classes.

This change does not include the Java 8-incompatible syntax.

Test: Built a debug image and ran one iteration of MPTS.  Verified that no
errors were seen.

Change-Id: I67b1cd3a151f4dc037c35f93f341a5de3e023941