[FZ Editor] Set layout size and position by percent (image included)

[daetanbhuck]

Description of the new feature / enhancement

When editing layouts, select a layout to set its relative size and position.

The linked image (below) shows a settings dialog with three panes. The pane "Sequence in per cent" lists the windows x and y positions, widths, and heights as a percent of screen size and options to add, edit, or delete the selected entry. (The linked image is a screenshot from WinSplit Revolution, a discontinued window manager.)

Scenario when this would be used?

This feature allows precise and accurate control of window layout in canvas mode using relative positioning. This is especially useful when the pixel count of a relative placement is not known.

As a power user, I can more quickly place a window "at x = 50% and y = 10% with width = 40% and height = 40%" to make a nicely padded window placement. However, I don't know what those percents are in absolute pixels for 4K, let alone any other resolution.

Supporting information

Linked image.

[daetanbhuck]

Duplicate of #463