Java 6 changed CollationKey from final to abstract.

I've also taken the opportunity to tidy up our implementation a little,
though my hands are tied by (a) the fact that our concrete classes are
in a separate package from our abstract classes and (b) frameworks/base
actually pokes about with our icu4jni collation code (http://b/2417080).

I've also tidied up a bunch of dead code. In particular, it's silly for
us to check parameters in Java that will be checked in native code (and
that one would assume will be valid most of the time anyway).

Bug: 1635883
Change-Id: I7db3c1ff1f0d23cb85604f9c8eb995e4488d7c0a
10 files changed