Restore editor state on reopen (#27672)

Closes https://github.com/zed-industries/zed/issues/11626
Part of https://github.com/zed-industries/zed/issues/12853

`"restore_on_file_reopen": true` in workspace settings can now be used
to enable and disable editor data between file reopens in the same pane:


https://github.com/user-attachments/assets/8d938ee1-d854-42a8-bbc3-2a4e4d7d5933

The settings are generic and panes' data store can be extended for
further entities, beyond editors.

---------------
Impl details: 

Currently, the project entry IDs seem to be stable across file reopens,
unlike BufferIds, so those were used.
Originally, the DB data was considered over in-memory one as editors
serialize their state anyway, but managing and exposing PaneIds out of
the DB is quite tedious and joining the DB data otherwise is not
possible.


Release Notes:

- Started to restore editor state on reopen

crates/workspace/src/workspace_settings.rs

@@ -17,6 +17,7 @@ pub struct WorkspaceSettings {
     pub show_call_status_icon: bool,
     pub autosave: AutosaveSetting,
     pub restore_on_startup: RestoreOnStartupBehavior,
+    pub restore_on_file_reopen: bool,
     pub drop_target_size: f32,
     pub use_system_path_prompts: bool,
     pub use_system_prompts: bool,
@@ -134,6 +135,15 @@ pub struct WorkspaceSettingsContent {
     /// Values: none, last_workspace, last_session
     /// Default: last_session
     pub restore_on_startup: Option<RestoreOnStartupBehavior>,
+    /// Whether to attempt to restore previous file's state when opening it again.
+    /// The state is stored per pane.
+    /// When disabled, defaults are applied instead of the state restoration.
+    ///
+    /// E.g. for editors, selections, folds and scroll positions are restored, if the same file is closed and, later, opened again in the same pane.
+    /// When disabled, a single selection in the very beginning of the file, zero scroll position and no folds state is used as a default.
+    ///
+    /// Default: true
+    pub restore_on_file_reopen: Option<bool>,
     /// The size of the workspace split drop targets on the outer edges.
     /// Given as a fraction that will be multiplied by the smaller dimension of the workspace.
     ///