[release/6.0] Fixes #62167. WriteAsync may truncate data if called after .Advance(int)#62348

safern merged 2 commits intorelease/6.0dotnet/runtime:release/6.0from

backport/pr-62306-to-release/6.0dotnet/runtime:backport/pr-62306-to-release/6.0Copy head branch name to clipboard