Support filtering the files view to only show files with comments

• As noted in microsoft/vscode#252168, I have a PR with a sizable number of comments spread across some sizable number of files, but it's a fairly small subset of all files in the repository.

I'd like to be able to filter the Pull Requests pane to only show files with comments. Currently, I have:

And this comments pane:

Sure, I could highlight the first file in the comments pane, and then press the left arrow and then the down arrow and alternate through left and down until I got to the end, but it's fairly painful, and I don't get access to the pretty file hierarchy:

从 Pull Requests 窗格开始，找到文件视图以及其中现有的评论相关数据或控件。确定该视图如何表示文件和评论，然后让筛选器仅显示包含评论的文件，同时保留文件层级；如果相关入口点已有测试覆盖，则添加或更新测试。