Improve URI.equals performance.

The main improvement is that we're vastly reducing
the amount of garbage this method creates.

Also, get rid of some incorrect checks and add a new
benchmark test case.

Before vs. After:

URI                            Equals     1540.1 =
URI EqualsWithHeavilyEscapedComponent 11921397.1 ==============================

URI                            Equals     1337.2 =
URI EqualsWithHeavilyEscapedComponent   588934.3 ==============================

Change-Id: I9ddb87b8267f0ac6a3ac85c2989cc0dd305ef6a1