[sznowicki]

This PR removes onClick logic from Thumbnail, which after debugging a problem with not being able to longpress on a thumbnail to upvote/downvote seems to be actually obsolute since it the only usage of that onClick action is to open post, which when the entire thing is not handled by Thumbnail, is handled by the parent Item with exactly same action.

Thumbnail.interactive was de-facto always true, so I made a call and removed it all which in result:

1. Makes it possible to long press on an Item, even when touching the actual Thumbnail (previously was less likely to happen, before 100% width thumbnails).
2. Maintains previous action on short press (opens the post).