Implement code sinking.

Implement code sinking.

Small example of what the optimization does:

Object o = new Object();
if (test) {
  throw new Error(o.toString());
}

will be turned into (note that the first user of 'o'
is the 'new Error' allocation which has 'o' in its
environment):
if (test) {
  Object o = new Obect();
  throw new Error(o.toString());
}

There are other examples in 639-checker-code-sinking.

Ritz individual benchmarks improve on art-jit-cc from
5% (EvaluateComplexFormulas) to 23% (MoveFunctionColumn)
on all platforms.

Test: 639-checker-code-sinking
Test: test-art-host
Test: borg job run
Test: libcore + jdwp

bug:35634932
bug:30933338

Change-Id: Ib99c00c93fe76ffffb17afffb5a0e30a14310652