* Add strikethrough to deleted file tree item in history file tree
* Add "restore file" button on toolbar if the selected file have a `removed` operation.
* Implement "restore file" functionality on removed file:
- Refactor the `Selection` object in history context value since we need the `deletedAtV` data which currently is not passed through the state.
- Refactor and clean up file tree type system to support passing through the whole `FileDiff` object for getting the `deletedAtV` data which only appear on `removed` operation
- Implement `postJSON` with file restoration API and pass it on restore file onClick handler at toolbar
* Implement loading behaviour while restoring file is inflight:
- Add `loadingRestoreFile` to `LoadingState`
- Change restore file button to `Restoring...` when in loading state.
* Refactor:
- Rename `DiffOperation` to `FileOperation`
- Extract `isFileRemoved` and `isFileRenamed` to its own file
- Extract `Toolbar` components into small files
GitOrigin-RevId: 2e32ebd2165f73fc6533ff282a9c084162efd682
