Avoid unnecessary DB writes (#29417)

Part of https://github.com/zed-industries/zed/issues/16472

* Adds debug logging to everywhere near INSERT/UPDATEs in the DB

So something like 
`env RUST_LOG=debug,wasmtime_cranelift=off,cranelift_codegen=off,vte=off
cargo run` could be used to view these (current zlog seems to process
the exclusions odd, so not sure this is the optimal RUST_LOG line) can
be used to debug any further writes.

* Removes excessive window stack serialization

Previously, it serialized unconditionally every 100ms.
Now, only if the stack had changed, which is now check every 500ms.

* Removes excessive terminal serialization

Previously, it serialized its `cwd` on every `ItemEvent::UpdateTab`
which was caused by e.g. any character output.
Now, only if the `cwd` has changed at the next event processing time.

Release Notes:

- Fixed more excessive DB writes

crates/image_viewer/Cargo.toml

@@ -21,6 +21,7 @@ db.workspace = true
 editor.workspace = true
 file_icons.workspace = true
 gpui.workspace = true
+log.workspace = true
 project.workspace = true
 schemars.workspace = true
 serde.workspace = true

crates/image_viewer/src/image_viewer.rs

@@ -261,6 +261,7 @@ impl SerializableItem for ImageView {
 
         Some(cx.background_spawn({
             async move {
+                log::debug!("Saving image at path {image_path:?}");
                 IMAGE_VIEWER
                     .save_image_path(item_id, workspace_id, image_path)
                     .await
@@ -399,18 +400,6 @@ mod persistence {
     }
 
     impl ImageViewerDb {
-        query! {
-           pub async fn update_workspace_id(
-                new_id: WorkspaceId,
-                old_id: WorkspaceId,
-                item_id: ItemId
-            ) -> Result<()> {
-                UPDATE image_viewers
-                SET workspace_id = ?
-                WHERE workspace_id = ? AND item_id = ?
-            }
-        }
-
         query! {
             pub async fn save_image_path(
                 item_id: ItemId,