style: Fix icon and text scaling support for a11y; standardize padding
This is a pretty wide-ranging update to help address shortcomings/bugs with scaling when folks use the Large Text feature as well as make elements use common padding and margin values.
- new drawing function to convert px to em, for select instances
- updated fontsize function to convert fonts in pt to em; replace/update instances of labels not using fontsize()
- replace instances of discrete margin and padding sizes with defined values and a multiplier
- fix instances where assets or icons did not scale along with text
- rework panel buttons to accommodate the scaling padding and icons
- new 'scalable' definitions for padding and icons to use in elements that follow text scaling
Fixes #7219 (closed), #7220 (closed), #5418 (closed), #3918 (closed)
Edited by Sam Hewitt