Create a new IMAP Server Info dialog.
The old dialog was based on a QMessageBox::Information. This has no
support for scrollbars, except using a detailed text which does not
support HTML formatting.
The new dialog is based on the About Trojita dialog, with a scrollable
list of server capabilities.
Change-Id: I14ba8ffe5346ae352c5994a45e875c76fa43b82c
GUI:
BUG: 406417