Enable multi-reg LONG nodes on 32 bit

[SingleAccretion]

Or, rather, enable promotion of multi-reg LONG variables, unblocking field enregistration.

The diffs (x86) are nice and simple:

-       mov      dword ptr [esp], eax
-       mov      dword ptr [esp+04H], edx
-       mov      eax, dword ptr [esp]
-       mov      edx, dword ptr [esp+04H]
        add      eax, -1
        adc      edx, -1

And also numerous (-35K for the benchmarks collection on x86).

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Issue Details

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Or, rather, enable promotion of multi-reg LONG variables, unblocking field enregistration.

The diffs are nice and simple:

-       mov      dword ptr [esp], eax
-       mov      dword ptr [esp+04H], edx
-       mov      eax, dword ptr [esp]
-       mov      edx, dword ptr [esp+04H]
        add      eax, -1
        adc      edx, -1

And also numerous (-35K for the benchmarks collection on x86).

Author:	SingleAccretion
Assignees:	-
Labels:	area-CodeGen-coreclr
Milestone:	-

[SingleAccretion]

@dotnet/jit-contrib

[AndyAyersMS]

@TIHan perhaps you can review this one?

[kunalspathak]

A nit comment and a question.

[kunalspathak]

I am not able to see arm Release failures. Tried rerunning the jobs, but they are not getting scheduled. Do you remember what the failure was?

[SingleAccretion]

No, unfortunately... Let's rerun the whole CI to get fresher coverage.

[SingleAccretion]

GH doesn't show it, but Libraries Build arm Release succeeded: https://dev.azure.com/dnceng-public/public/_build/results?buildId=61503&view=logs&j=fbba4562-0196-5144-0bc8-97e5ecde48bd.