Modify Diff View FileTree to show all files
## Changes
* removes Show Status button on diff
* uses `git diff-tree` to generate the file tree for the diff
* doesn't reload the diff tree each time we load more files in the
preview
* selecting and unloaded file will keep loading until that file is
loaded
* removes `DiffFileList.vue` and "Show Stats" in diff options
## Open Questions
* selecting and unloaded file will keep loading until that file is
loaded. Is this behaviour okay? It matches what github does.
### Demo
In this demo I set `git.MAX_GIT_DIFF_FILES=1` in my `app.ini` to
demonstrate a worst case example. In most cases the behaviour isn't
nearly as jarring as we load a bunch of files at a time.
https://github.com/user-attachments/assets/72f29663-d6fc-472d-94fa-7fb5950c2836
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Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
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