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

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

Opening all artists from a genre was never implemented even though a
test was supposed to exist. Fix that.

BUG: 419145

seems that reusing the menu exported for the global menu is a very bad
idea

using a menu as a child of the system tray icon seems to be the
solution

BUG: 409010
CCBUG: 419145

BUG: 418296

BUG: 418576

fix wrong data being displayed in metadata window or context view if
showing a track during database import of tracks

use a base 64 encoded data url with inline image data

BUG: 416131

BUG: 416170

allow users to workaround missing music files in Baloo index by
configuring Elisa not to rely only on it.

BUG: 417822