fix: Process Chokidar events batches sequentially

[taratatach]

We buffer events emitted by Chokidar as the underlying FSEvents API, on macOS, can add delay between events relating to the same document and processing the first events without the latter ones can lead to wrong assumptions about what changes were actually made.

Buffered events are then flushed 10 seconds after the last event was buffered (i.e. each buffered event resets the 10 seconds delay).

Since this process is asynchronous and is only time-based, we can end up flushing buffered events while some previous batch is still being processed, creating situations where unexpected behavior can happen.

To prevent this, we now prevent any buffer flushes while a batch is being processed and restore the flushing timeout once finished. This can add a small delay to the next batch processing but since we don't know if already buffered events could be flushed at that point it seems safer.

Please make sure the following boxes are checked:

• [x] PR is not too big
• [x] it improves UX & DX in some way
• [ ] it includes unit tests matching the implementation changes
• [ ] it includes scenarios matching a new behaviour or has been manually tested
• [ ] it includes relevant documentation

[taratatach]

Closing in favor of #2325.