AdvSimd support for System.Text.Unicode.Utf8Utility.TranscodeToUtf8 (#39041)
* AdvSimd support for System.Text.Unicode.Utf8Utility.TranscodeToUtf8
* Readd using to prevent build failure.
Add AdvSimd equivalent operation to TestZ.
* Inverted condition
* Address IsSupported order, improve use ExtractNarrowingSaturated usage
* Rename source to result, second argument utf16Data
* Improve CompareTest
* Add shims causing failures in Linux
* Use unsigned version of ExtractNarrowingSaturate, avoid using MinAcross and use MaxPairwise instead
* Missing support check for Sse2.X64
* Add missing case for AdvSimd
* Use MinPairwise for short