Scale UI elements in the editor based on the buffer_font_size (#11817)
This PR adjusts how UI elements are rendered inside of full-size editors
to scale with the configured `buffer_font_size`.
This fixes some issues where UI elements (such as the `IconButton`s used
for code action and task run indicators) would not scale as the
`buffer_font_size` was changed.
We achieve this by changing the rem size when rendering the
`EditorElement`, with a rem size that is derived from the
`buffer_font_size`.
`WindowContext` now has a new `with_rem_size` method that can be used to
render an element with a given rem size. Note that this can only be
called during `request_layout`, `prepaint`, or `paint`, similar to
`with_text_style` or `with_content_mask`.
### Before
<img width="1264" alt="Screenshot 2024-05-14 at 2 15 39 PM"
src="https://github.com/zed-industries/zed/assets/1486634/05ad7f8d-c62f-4baa-bffd-38cace7f3710">
<img width="1264" alt="Screenshot 2024-05-14 at 2 15 49 PM"
src="https://github.com/zed-industries/zed/assets/1486634/254cd11c-3723-488f-ab3d-ed653169056c">
### After
<img width="1264" alt="Screenshot 2024-05-14 at 2 13 02 PM"
src="https://github.com/zed-industries/zed/assets/1486634/c8dad309-62a4-444f-bfeb-a0009dc08c03">
<img width="1264" alt="Screenshot 2024-05-14 at 2 13 06 PM"
src="https://github.com/zed-industries/zed/assets/1486634/4d9a3a52-9656-4768-b210-840b4884e381">
Note: This diff is best viewed with whitespace changes hidden:
<img width="245" alt="Screenshot 2024-05-14 at 2 22 45 PM"
src="https://github.com/zed-industries/zed/assets/1486634/7cb9829f-9c1b-4224-95be-82182017ed90">
Release Notes:
- Changed UI elements within the editor to scale based on
`buffer_font_size` (e.g., code action indicators, task run indicators,
etc.).
Marshall Bowers
5b8bb6237f