Use on-the-fly detection of posts and abandon the pre-populated conversion queue mechanism

[iuravic]

Describe the solution you'd like
Abandon the pre-populated "conversion queue" mechanism, and switch to an on-the-fly detection of Posts for conversion -- the branch try/insert-at-convert-time already contains the proof of concept, use this instead.

Describe alternatives you've considered
The on-the-fly mechanism will be a bit slower, but simpler. Since this plugin is typically run only once on a site, trading a bit of efficiency for increased simplicity seems like the right way to go.