Allow configuring spacing of project panel entries (#16255)

Release Notes:

- Added `project_panel.entry_spacing` setting to configure spacing
between entries in the project panel.

### Comfortable (default)
```json
  "project_panel": {
    "entry_spacing": "comfortable",
```
<img width="1582" alt="Screenshot 2024-08-14 at 5 50 41 PM"
src="https://github.com/user-attachments/assets/3411a82e-7517-4095-bf4a-bbf40000a7cb">

### Standard
```json
  "project_panel": {
    "entry_spacing": "standard",
```
<img width="1582" alt="Screenshot 2024-08-14 at 5 50 54 PM"
src="https://github.com/user-attachments/assets/2c13d799-c405-4301-8214-1cb3cc641c92">

---------

Co-authored-by: Marshall Bowers <elliott.codes@gmail.com>

crates/ui/src/components/list/list_item.rs

@@ -11,6 +11,7 @@ use crate::{prelude::*, Disclosure};
 pub enum ListItemSpacing {
     #[default]
     Dense,
+    ExtraDense,
     Sparse,
 }
 
@@ -219,6 +220,7 @@ impl RenderOnce for ListItem {
                     .px(DynamicSpacing::Base06.rems(cx))
                     .map(|this| match self.spacing {
                         ListItemSpacing::Dense => this,
+                        ListItemSpacing::ExtraDense => this.py_neg_px(),
                         ListItemSpacing::Sparse => this.py_1(),
                     })
                     .when(self.inset && !self.disabled, |this| {