optimizing: Build HConstructorFence for HNewArray/HNewInstance nodes

Also fixes:
* LSE, code_sinking to keep optimizing new-instance if it did so before
* Various tests to expect constructor fences after new-instance

Sidenote: new-instance String does not get a ConstructorFence; the
special StringFactory calls are assumed to be self-fencing.

Metric changes on go/lem:
* CodeSize -0.262% in ART-Compile (ARMv8)
* RunTime -0.747% for all (linux-armv8)

(No changes expected to x86, constructor fences are no-op).

The RunTime regression is temporary until art_quick_alloc_* entrypoints have their
DMBs removed in a follow up CL.

Test: art/test.py
Bug: 36656456
Change-Id: I6a936a6e51c623e1c6b5b22eee5c3c72bebbed35