Fix loop optimization in the presence of environment uses.

We should not remove instructions that have deoptimize as
users, or that have environment uses in a debuggable setup.

bug: 62536525
bug: 33775412
Test: 656-loop-deopt
Change-Id: Iaec1a0b6e90c6a0169f18c6985f00fd8baf2dece
5 files changed