Use an internal index to more accurately track renames on macOS

When a file is moved and we're using the native FSEvents API on macOS, it issues native events with flag ITEM_RENAMED set, but not flags ITEM_CREATED or ITEM_REMOVED. Typical cases include:

1. Moving a file within the watch scope. In this case, there are two native events: one for the source (logically: delete), and one for the destination (logically: create).
2. Moving a file into the watch scope. In this case, there is one native event, for the destination (logically: create).
3. Moving a file out of the watch scope. In this case, there is one native event, for the source (logically: delete).

Because flags ITEM_CREATED and ITEM_REMOVED aren't set, the native events in cases 2 and 3 are indistinguishable. Currently, this is solved by asking the file system if the file exists: if it does, we assume it's case 2; if it doesn't, we assume it's case 3. However, this can be inaccurate (because things can have happened to the file between the native event was issued and asking the file system). A more accurate approach could be to maintain our own index.

Bắt đầu bằng cách truy vết việc xử lý macOS FSEvents và cách ITEM_RENAMED, ITEM_CREATED và ITEM_REMOVED hiện đang được diễn giải. Tái hiện ba trường hợp di chuyển được mô tả trong issue, sau đó xác định việc hoàn thành là phân biệt được các lần di chuyển vào, ra khỏi và bên trong phạm vi theo dõi mà không chỉ dựa vào việc kiểm tra sự tồn tại trên hệ thống tệp.