Rework of info page, now unified for both users and groups

this is how it looks now (first commit)

I chose to use Loaders s.t. I can load only items that actually have something to show and to avoid to put check condition in fields like text, to avoid accessing undefined properties.

Known issues / todo:

• bot description isn't shown (issue with backend, haven't looked at it yet, I just edited qml) EDIT: my fault, it was just a different property
• make a dedicated page for the hash key verification for secret chats
• I often get qrc:/pages/ChatInfoPage.qml:207:13: QML Loader: Binding loop detected for property "active" with users only (idk how to solve it) EDIT: solved with Loaders removal
• invite link for basic groups is shown (the one which looks like t.me/joinchat/CWb6A1Ru8gblablabla) but it isn't for supergroups (which looks like t.me/ubports) EDIT: had to get the username of the supergroup
• using ListItem is handy for divider and onClicked signal but they have issues with the height which I can't make change reliably if the content needs to be wrapped. I removed it for the description (using a plain Item instead of ListItem had issues too so I used SlotsLayout directly) as it is usually very long but it is still used for the invite link
• consider the use of a Repeater and a ListModel because a lot of the code repeated here is pretty much the same

fixes #76 (closed)