This PR changes the way a horizontal margin is added in editors. It
removes the possibility to set a custom `horizontal_padding` for an
editor and utilizes the default `gutter_dimension` instead.

This change is made to ensure that no issues with soft-wrapping occurs
for any editor that has a `horizontal_margin` set (see #26893 for more
context on the implications here`. Furthermore, it ensures that the text
actually renders properly when scrolling horizontally and is not
cut-off.

### Horizontal padding:

| `main` | This PR |
| --- | --- |
| ![main
padding](https://github.com/user-attachments/assets/4e7ea020-f92d-4f28-8cc1-89d0b0350683)
| ![PR
padding](https://github.com/user-attachments/assets/a05bae17-c384-431b-bb79-a1fffe7a29d7)
|

### Editor horizontally scrolled:

| `main` | This PR |
| --- | --- |
| ![main
scrolled](https://github.com/user-attachments/assets/1a30156f-6c08-4cf9-94aa-9d087c0408cc)
| ![pr
scrolled](https://github.com/user-attachments/assets/d0daa72e-3b02-479b-aea0-41e1a376c567)
|

Notice the difference at the horizontal borders.

The margin added for the `edit_file_tool` was 4 pixels. The `descent`,
whilst not exactly, is roughly the same here and also scales with the
font size nicely. Furthermore, it seems that the
`gutter_dimensions.margin` should be present anyway, given the following
comment


https://github.com/zed-industries/zed/blob/0b00256f5884fd17b4f834730b31f365613f3683/crates/editor/src/element.rs#L6887-L6889

so ensuring this property is actually set and not 0 seems to be
reasonable given the circumstances.

Please note though that this will apply to all editors in the app.
Again, this seems like it should be the case anyway, just wanted to
mention this again.

Should the fix like this not be wanted, I can change this here so that
the `horizontal_margin` is better accounted for when soft-wrapping in an
editor. Feel free to let me know in this case.

Release Notes:

- N/A