Expand the selection outline on draw shapes according to pen thickness
when only one shape is selected.
Right now the outline of many of our shapes don't take stroke thickness
into account. This is a pretty hard thing to get right, so in the short
term here's a fix for one of the most common places this is an issue:
selecting a single horizontal/vertical draw shape. This fix isn't
perfect: resizing gets slightly janky when you completely flip the shape
- see how the handle leaves the cursor behind in the gif when that
happens. We can revisit with a more comprehensive solution later.
This is pulled out from the highlighter work! The highlighter shape will
use the shape APIs added here.
### Change Type
- [x] `patch` — Bug Fix
### Test Plan
1. Create a draw shape
2. Select it
3. Selection bounds should include the stroke width
4. Add another shape to the selection
5. Selection bounds should no longer include the stroke width
### Release Notes
- Improve selection outlines around horizontal or vertical draw shapes
cd8c92779d