Replace GsPluginFailureFlags with a simple interactivity boolean

This allows the front-end code to specify if this was in response to the user
clicking a button rather than being a background task. Nobody really understood
how GsPluginFailureFlags was supposed to work -- which meant there were bugs
everywhere.

It's all a lot simpler now.
1 job for <span class="ref-name">wip/hughsie/GsPluginInteractivity</span> in 5 minutes and 46 seconds (queued for 7 seconds)
Status Job ID Name Coverage
  Build
passed #66233
build-gnome-software

00:05:46