Clean-up sharpening and compiler driver.

Remove dependency on compiler driver for sharpening
and dex2dex (the methods called on the compiler driver were
doing unnecessary work), and remove the now unused methods
in compiler driver.

Also remove test that is now invalid, as sharpening always
succeeds.

test: m test-art-host m test-art-target
Change-Id: I54e91c6839bd5b0b86182f2f43ba5d2c112ef908