ART: Do not attempt to compile a method with too many registers

The mir_graph has a hard limit on how many ssa registers it can
handle, and will silently fail or fatal out in debug builds when
more SSA registers are necessary. This adds a check in the frontend
that tries to catch some of these cases, and makes the DCHECK a
CHECK to not silently fail.

Bug: 16018097
Change-Id: Iad82178945a8f8c34943cc7573fd73d2b4decade