Add preview tabs (#9125)

This PR implements the preview tabs feature from VSCode.
More details and thanks for the head start of the implementation here
#6782.

Here is what I have observed from using the vscode implementation ([x]
-> already implemented):
- [x] Single click on project file opens tab as preview
- [x] Double click on item in project panel opens tab as permanent
- [x] Double click on the tab makes it permanent
- [x] Navigating away from the tab makes the tab permanent and the new
tab is shown as preview (e.g. GoToReference)
- [x] Existing preview tab is reused when opening a new tab
- [x] Dragging tab to the same/another panel makes the tab permanent
- [x] Opening a tab from the file finder makes the tab permanent
- [x] Editing a preview tab will make the tab permanent
- [x] Using the space key in the project panel opens the tab as preview
- [x] Handle navigation history correctly (restore a preview tab as
preview as well)
- [x] Restore preview tabs after restarting
- [x] Support opening files from file finder in preview mode (vscode:
"Enable Preview From Quick Open")
 
I need to do some more testing of the vscode implementation, there might
be other behaviors/workflows which im not aware of that open an item as
preview/make them permanent.

Showcase:


https://github.com/zed-industries/zed/assets/53836821/9be16515-c740-4905-bea1-88871112ef86


TODOs
- [x] Provide `enable_preview_tabs` setting
- [x] Write some tests
- [x] How should we handle this in collaboration mode (have not tested
the behavior so far)
- [x] Keyboard driven usage (probably need workspace commands)
- [x] Register `TogglePreviewTab` only when setting enabled?
- [x] Render preview tabs in tab switcher as italic
- [x] Render preview tabs in image viewer as italic
- [x] Should this be enabled by default (it is the default behavior in
VSCode)?
- [x] Docs

Future improvements (out of scope for now):
- Support preview mode for find all references and possibly other
multibuffers (VSCode: "Enable Preview From Code Navigation")


Release Notes:

- Added preview tabs
([#4922](https://github.com/zed-industries/zed/issues/4922)).

---------

Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>

crates/image_viewer/src/image_viewer.rs

@@ -11,7 +11,7 @@ use project::{Project, ProjectEntryId, ProjectPath};
 use std::{ffi::OsStr, path::PathBuf};
 use util::ResultExt;
 use workspace::{
-    item::{Item, ProjectItem},
+    item::{Item, ProjectItem, TabContentParams},
     ItemId, Pane, Workspace, WorkspaceId,
 };
 
@@ -72,12 +72,7 @@ pub struct ImageView {
 impl Item for ImageView {
     type Event = ();
 
-    fn tab_content(
-        &self,
-        _detail: Option<usize>,
-        selected: bool,
-        _cx: &WindowContext,
-    ) -> AnyElement {
+    fn tab_content(&self, params: TabContentParams, _cx: &WindowContext) -> AnyElement {
         let title = self
             .path
             .file_name()
@@ -86,11 +81,12 @@ impl Item for ImageView {
             .to_string();
         Label::new(title)
             .single_line()
-            .color(if selected {
+            .color(if params.selected {
                 Color::Default
             } else {
                 Color::Muted
             })
+            .italic(params.preview)
             .into_any_element()
     }