Limit the maximum number of avatars shown for other user read markers and collapsed state events
For state events \

For read markers \

Unread count is deprecated and notification count should be used in all cases. As such remove unreadCount and use notification count in all places it was being used.
Fixesnetwork/neochat#76 \
BUG: 466515
This move the finding of links and the creation of a `linkpreviewer` into c++.
- The links are now extracted from the text in `texthandler`
- The `messageeventmodel` now creates and stores `linkpreviewers` for events that have links in the current room.
Two new model roles have been created to let a text delegate know when the link preview should be shown (`showLinkPreview`) and pass the link previewer (`linkPreviewer`). Empty link previewer are returned where link don't exist so the qml doesn't have to have checks for whether the parameters are undefined.
Further improvements to the handling of `mediaInfo` in `messageeventmodel`.
`blurhash` and `thumbnailInfo` are now replaced with a single `tempInfo` object that contains a single temp source. The priority is thumbnail > `blurhash` > empty if none exist.
Fixesnetwork/neochat#235
Create a `messageeventmodel` role for media info and reply media info that is a QMap with all the required data.
This replaces the MediaUrlRole, FileMimeTypeRole and the ContentTypeRole. The reply role no longer needs the content role.
This also ensures mxc urls are now generated for replies. All the media parameters will now have default values assigned in the model so the QML no longer needs to do this.