preview tabs: Allow replacing preview tab when using code navigation (#10730)

This PR adds support for replacing the current preview tab when using
GoToDefinition. Previously a tab, that was navigated away from, was
converted into a permanent tab and the new tab was opened as preview.

Without `enable_preview_from_code_navigation`:


https://github.com/zed-industries/zed/assets/53836821/99840724-d6ff-4738-a9c4-ee71a0001634

With `enable_preview_from_code_navigation`:


https://github.com/zed-industries/zed/assets/53836821/8c60efcb-d597-40bf-b08b-13faf5a289b6

Note: In the future I would like to improve support for the navigation
history, because right now tabs that are not "normal" project items,
e.g. FindAllReferences cannot be reopened

Release Notes:

- Added support for replacing the current preview tab when using code
navigation (`enable_preview_from_code_navigation`)

crates/activity_indicator/src/activity_indicator.rs

@@ -99,6 +99,7 @@ impl ActivityIndicator {
                         Box::new(
                             cx.new_view(|cx| Editor::for_buffer(buffer, Some(project.clone()), cx)),
                         ),
+                        None,
                         cx,
                     );
                 }