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/component_preview/src/persistence.rs

@@ -23,6 +23,9 @@ impl ComponentPreviewDb {
         workspace_id: WorkspaceId,
         active_page_id: String,
     ) -> Result<()> {
+        log::debug!(
+            "Saving active page: item_id={item_id:?}, workspace_id={workspace_id:?}, active_page_id={active_page_id}"
+        );
         let query = "INSERT INTO component_previews(item_id, workspace_id, active_page_id)
             VALUES (?1, ?2, ?3)
             ON CONFLICT DO UPDATE SET