This adds new code stubs for abstract relational comparison,
namely LessThanStub, LessThanOrEqualStub, GreaterThanStub and
GreaterThanOrEqualStub, and hooks them up for Ignition and TurboFan.
These stubs implement the full compare operation without any
unpredictable bailouts. Currently they still go to C++ for string
comparisons, and also use the %ToPrimitive_Number runtime entry, as
we still lack a stub for the ToPrimitive operation. These issues
will be addressed separately in follow-up CLs.

Drive-by-fix: Add support for deferred code in the RawMachineAssembler
and CodeStubAssembler. A block can be marked as deferred by marking its
Label as deferred, which will then make the register allocator penalize
this block and prefer better register assignments for the other blocks.

R=epertoso@chromium.org

Review URL: https://codereview.chromium.org/1759133002

Cr-Commit-Position: refs/heads/master@{#34463}