`py list --online --one` doesn't account for platform

If I `py list --one <TAG>` then it shows the runtime that is going to be selected when I run.

However, if I `py list --online --one <TAG>` then it ignores the default platform and shows the very first (e.g. `-32` even on a `-64` platform).

We should filter the online list so that the current platform comes first, at least when the `--one` option is set.