Describe the bug

When a user is automatically opted into using the block editor as a part of the progressive rollout we do not record any analytics event.

In particular, if you check the wpandroid_gutenberg_enabled event, it has not increased since the progressive rollout started, and it has no events with a source indicating the block editor was enabled as a part of the progressive rollout.

Expected behavior

When a user is automatically opted into using the block editor as a part of the progressive rollout, we should send off a wpandroid_gutenberg_enabled event with a source value of on_progressive_rollout.

We have a BlockEditorEnabledSource enum with an ON_PROGRESSIVE_ROLLOUT value, but that value appears to not be used. I believe we can get the analytics we want by adding a call along these lines to the progressive rollout code:

AnalyticsUtils.trackWithSiteDetails(
  EDITOR_GUTENBERG_ENABLED, 
  site, 
  ON_PROGRESSIVE_ROLLOUT.asPropertyMap()
);