editor: Add minimap (#26893)

## Overview

This PR adds the minimap feature to the Zed editor, closely following
the [design from Visual Studio
Code](https://code.visualstudio.com/docs/getstarted/userinterface#_minimap).
When configured, a second instance of the editor will appear to the left
of the scrollbar. This instance is not interactive and it has a slimmed
down set of annotations, but it is otherwise just a zoomed-out version
of the main editor instance. A thumb shows the line boundaries of the
main viewport, as well as the progress through the document. Clicking on
a section of code in the minimap will jump the editor to that code.
Dragging the thumb will act like the scrollbar, moving sequentially
through the document.

![screenshot of Zed with three editors open and the minimap enabled,
showing the
slider](https://github.com/user-attachments/assets/4178d23a-a5ea-4e38-b871-06dd2a8f9560)

## New settings

This adds a `minimap` section to the editor settings with the following
keys:

### `show`

When to show the minimap in the editor.
This setting can take three values:
1. Show the minimap if the editor's scrollbar is visible: `"auto"`
2. Always show the minimap: `"always"`
3. Never show the minimap: `"never"` (default)

### `thumb`

When to show the minimap thumb.
This setting can take two values:
1. Show the minimap thumb if the mouse is over the minimap: `"hover"`
2. Always show the minimap thumb: `"always"` (default)

### `width`

The width of the minimap in pixels.

Default: `100`

### `font_size`

The font size of the minimap in pixels.

Default: `2`

## Providing feedback

In order to keep the PR focused on development updates, please use the
discussion thread for feature suggestions and usability feedback: #26894


## Features left to add

- [x] fix scrolling performance
- [x] user settings for enable/disable, width, text size, etc.
- [x] show overview of visible lines in minimap
- [x] clicking on minimap should navigate to the corresponding section
of code
- ~[ ] more prominent highlighting in the minimap editor~
- ~[ ] override scrollbar auto setting to always when minimap is set to
always show~

Release Notes:

- Added minimap for high-level overview and quick navigation of editor
contents.

---------

Co-authored-by: MrSubidubi <dev@bahn.sh>
Co-authored-by: Kirill Bulatov <kirill@zed.dev>

crates/repl/src/session.rs

@@ -93,6 +93,7 @@ impl EditorBlock {
                 style: BlockStyle::Sticky,
                 render: Self::create_output_area_renderer(execution_view.clone(), on_close.clone()),
                 priority: 0,
+                render_in_minimap: false,
             };
 
             let block_id = editor.insert_blocks([block], None, cx)[0];
@@ -126,7 +127,8 @@ impl EditorBlock {
             let execution_view = execution_view.clone();
             let text_style = crate::outputs::plain::text_style(cx.window, cx.app);
 
-            let gutter = cx.gutter_dimensions;
+            let editor_margins = cx.margins;
+            let gutter = editor_margins.gutter;
 
             let block_id = cx.block_id;
             let on_close = on_close.clone();
@@ -184,7 +186,8 @@ impl EditorBlock {
                         .flex_1()
                         .size_full()
                         .py(text_line_height / 2.)
-                        .mr(gutter.width)
+                        .mr(editor_margins.right)
+                        .pr_2()
                         .child(execution_view),
                 )
                 .into_any_element()