[Task Manager] Ensure albumArtBackground and albumArtImage display at the same time
albumArtBackground and albumArtImage in tooltips sometimes do not display at the same time because of the slow network speed.
Now use ShaderEffect instead of a new Image instance as albumArtBackground to avoid the same file is read twice.
Note: After I update KDE related packages to git version, I find the unresponsiveness in grouped tooltips is gone, but the occasional unresponsiveness when hovering on the player icon for the first time still exists. So that issue should not be introduced in this MR.