Do not discard byref zeros in native int + byref additions

[SingleAccretion]

This should:

a) Ensure we're not "losing" the fact ADD produces a newly-born GC value (a mostly theoretical issue).
b) Reinstate the assert from #67600.

Diffs.

Fixes #67600.

[ghost]

Tagging subscribers to this area: @JulieLeeMSFT
See info in area-owners.md if you want to be subscribed.

Issue Details

---

This should:

a) Ensure we're not "losing" the fact a tree produced a newly-born GC value (a mostly theoretical issue).
b) Reinstate the assert from #67600.

We're not expecting significant diffs.

Author:	SingleAccretion
Assignees:	-
Labels:	area-CodeGen-coreclr, community-contribution
Milestone:	-

[SingleAccretion]

@dotnet/jit-contrib I would like to request a run of runtime-coreclr libraries-jitstress for this change.

[jakobbotsch]

/azp run runtime-coreclr libraries-jitstress

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[SingleAccretion]

Libraries stress "passed", so at least in the first approximation this fix should be sufficient.

Failures:

1. Linux_musl arm64 Debug: looks related to Segmentation fault in LibraryImportGenerator.Unit.Tests #67031.
2. OSX x64 checked: no existing issue, but does not look related (perhaps could be re-run).
3. Libraries stress, Linux arm Release: Assert failure: !CREATE_CHECK_STRING(pMT && pMT->Validate()) #67046.
4. Libraries stress, windows x86 Release: JSON flaky tests #67761.
5. Libraries stress, windows arm64 Release:
   • VM assert: looks like Test failure baseservices\\threading\\regressions\\beta2\\437017\\437017.cmd #67083.
   • UnauthorizedAccessException: pre-existing - earlier run.
   • Timeout: pre-existing - earlier run.

[SingleAccretion]

@dotnet/jit-contrib

[TIHan]

LGTM.