chatview: do not show full size images in the chat
Currently we display full-size pictures in the chatview. This is fine for a few ones, but when the chat grows over time the size of the conversation starts to cause major perfs issues.
With a reasonably sized conversation, Ring started to lag and my system had to swap:
Memory pressure relief: Total: res = 1190117376/1189875712/-241664, res+swap = 1186115584/1185832960/-282624
How to fix that:
- display compressed images
- display thumbnails