fix: Fix Chat drawer displayed under other drawers - MEED-7574 - Meed…

…s-io/MIPs#151 (#774)

Prior to this change, the chat drawer was always displayed under the other opened drawer due to CSS parent class selector 'miniChatDrawer' which has been made as mandatory in less files to make the Style applied. This change will just move all '.chatDrawer' CSS custom style outside of 'miniChatDrawer' parent selector and will delete the 'attached' attribute from 'exo-drawer' generic Vue component to allow displaying the drawer on top of the other already opened drawers (ex: Space Members Drawer from Space Home Page).