remove most of the ElisaUtils::PlayListEntryType parameters to allow
enqueue of miced entities

clean up also in MediaPlayListProxyModel

fix enqueue from grid views header bar

we were abusing TrackDataType for any kind of data leading to duplicated
arguments for managing the real type of the data due to that

This has to do with session management and the fact that when closed
the Elisa window hides and refuse to be closed when system tray icon
is configured active.

https://doc.qt.io/qt-5/qsessionmanager.html is the main input link in
the Qt documentation.

This patch detects that the session is being closed and allow the window
to be closed instead of hidden. That way, Elisa will not signal that the
window refused to close and the session manager will close the full
session.

remove LabelWithToolTip specific implementation that has not been made
to use Kirigami.Heading and that might not be needed

fix some compatibility issues related to the system tray icon support on
Linux

Kirigami has a standard component for this that results in a unified
appearance across KDE apps, and using it lets us remove tons of code.

(cherry picked from commit 3508b655)

The loader for this window was only becoming inactive when the
rejected() signal was emitted, but the window was not emitting that
signal when closed, which appears to have been the intention.

BUG: 420530
FIXED-IN: 20.04.1

The new maximized headerbar layour works great, but suffered from a few
papercut visual bugs, and the logic to implement it was unnecessarily
complicated in some cases. This patch simplifies the logic as much as
possible and fixes the layout bugs in the process.