2 small CQ optimizations.

[sandreenko]

Found during JitDoOldStructRetyping work.

Diffs are positive:

Crossgen CodeSize Diffs for System.Private.CoreLib.dll, framework assemblies for default jit
Summary of Code Size diffs:
(Lower is better)
Total bytes of diff: -31060 (-0.10% of base)
3169 total methods with Code Size differences (3167 improved, 2 regressed)
PMI CodeSize Diffs for System.Private.CoreLib.dll, framework assemblies for default jit
Summary of Code Size diffs:
(Lower is better)
Total bytes of diff: -40121 (-0.08% of base)
4964 total methods with Code Size differences (4952 improved, 12 regressed)

Need these changes to get rid of some regressions with !JitDoOldStructRetyping.

A simple diff example, -38 (-35.85% of base) : System.Private.CoreLib.dasm - Math:Truncate(Decimal):Decimal:
before

IN0001: 000008 mov ecx, dword ptr [rdx]
IN0002: 00000A mov dword ptr [V05 rsp+20H], ecx
IN0003: 00000E mov ecx, dword ptr [rdx+4]
IN0004: 000011 mov dword ptr [V06 rsp+24H], ecx
IN0005: 000015 mov ecx, dword ptr [rdx+8]
IN0006: 000018 mov dword ptr [V07 rsp+28H], ecx
IN0007: 00001C mov edx, dword ptr [rdx+12]
IN0008: 00001F mov dword ptr [V08 rsp+2CH], edx
IN0009: 000023 mov edx, dword ptr [V05 rsp+20H]

after:

IN0001: 000008 movups xmm0, xmmword ptr [rdx]
IN0002: 00000B movups xmmword ptr [V03 rsp+20H], xmm0
IN0003: 000010 mov edx, dword ptr [V05 rsp+20H]

[sandreenko]

found after Carol's similar change for block init #36146

[sandreenko]

PTAL @CarolEidt @dotnet/jit-contrib

[CarolEidt]

LGTM - thanks! and thanks for the detailed comments

[sandreenko]

The failures are known unrelated issues,