[release/8.0] Improve performance of UnmanagedMemoryStream#93812

carlossanlop merged 3 commits intorelease/8.0dotnet/runtime:release/8.0from

backport/pr-93766-to-release/8.0-stagingdotnet/runtime:backport/pr-93766-to-release/8.0-stagingCopy head branch name to clipboard