Revert "Revert "Iterative move coalescing for gc regalloc""

This reverts commit 6f61ee56,
and fixes the arena allocator issues in the original CL.
Functionality from the original CL has not changed.

Test: m valgrind-test-art-host-gtest-register_allocator_test
Test: ART_TEST_OPTIMIZING_GRAPH_COLOR=true m test-art-host-run-test

Change-Id: Idd979f4e03f0c2800e0c07a0a7d392c8a4230aab