desktop-shell: Click top left and align clock
Pads launchers with the empty space that used to be around them. Moving pointer to 0,0 and clicking launches the preferred app. First launcher has more padding at its start to look nice. Moves the clock to the right edge with same padding. Keeps one of the two values for text extents that the code was already retrieving but never read. Horizontal panel position centers the clock. Sets text in the panel, meaning tooltips and the clock, to consistent 14 units of the default system font at 85% of the max brightness, so it's less tiring on eyes.