UI ninepatch border geometry should match the borders in the layout (maybe)

## What problem does this solve or what need does it fill?

Borders created using the UI's texture slicing api aren't borders in the UI layout.
This means that for example that left-aligned text will align at the left edge of the uinode, not the inner edge of the border, and write over the ninepatch border:

## What solution would you like?

Have an option to draw borders from the UI layout using the ninepatch api.

## What alternative(s) have you considered?

You can add an invisable border the same size as the ninepatch border. This might be awkward to keep synchronised though.

The issue names no files, tests, or entry points; begin by locating the UI texture-slicing/ninepatch API and the layout border handling. Compare their geometry, clarify the intended option, and define completion with coverage showing that text alignment respects the ninepatch border.

Written by the indexing model from the issue text.