Derive icon paths (#17816)

This PR improves adding and working with icons by using the new
`DerivePathStr` to derive icon paths.

This means paths no longer need to be manually specified, and the
`IconName` and file name will always be consistent between icons.

This PR does not do any work to standardize icons visually, remove
unused icons, or any other such cleanup.

Release Notes:

- N/A

assets/icons/folder.svg

@@ -0,0 +1,3 @@
+<svg width="16" height="16" viewBox="0 0 16 16" fill="none" xmlns="http://www.w3.org/2000/svg">
+<path d="M8.26046 3.97337C8.3527 4.17617 8.4795 4.47151 8.57375 4.69341C8.65258 4.87898 8.83437 4.99999 9.03599 4.99999H12.5C12.7761 4.99999 13 5.22385 13 5.49999V12.125C13 12.4011 12.7761 12.625 12.5 12.625H3.5C3.22386 12.625 3 12.4011 3 12.125V3.86932C3 3.59318 3.22386 3.36932 3.5 3.36932H7.34219C7.74141 3.36932 8.09483 3.60924 8.26046 3.97337Z" stroke="black" stroke-width="1.5" stroke-linecap="round"/>
+</svg>