Purely cosmetic UI fixes

Summary:

• use the top automated toolbars, which will now be alwaysin toolbar mode, even in mobile mode
• search field in the top toolbar
• menu for adding rooms and channels on the channels list page, as is in the "global" context and not of the selected room
• online combo in a bottom statusbar
• channel title and favorite button on the top toolbar
• all toolbar buttons, out of header, in the toolbar
• the header component only has the topic and the optional user list
• bottom of the channel page in a toolbar with the same height of the channels bottom toolbar byu default (if there are messages it will

grow vertically)

• no padding for the channel page: so things get "cut" by toolbar separator lines rather than being cut into nothingness

Test Plan: Everything functions the same, all action that have been moved still trigger correctly

Reviewers: Ruqola, VDG, mlaurent, ngraham

Reviewed By: Ruqola, VDG, mlaurent, ngraham

Subscribers: mlaurent, ognarb, abetts, rooty, ngraham

Differential Revision: https://phabricator.kde.org/D19594