Improve Windows symlink instructions (#67029)

When the developer doesn't have permission to create symlinks, we
display specific instructions, but they were only correct for recent
versions of Windows 10. This improves them by:
- Giving the correct instructions for older versions.
- For recent versions, adds a command that will deep-link into the
  settings application so that developers don't have to figure out
  where/how to enable developer mode.

Fixes https://github.com/flutter/flutter/issues/66973