Avoid host filesystem permissions and polluting home folder as much as possible

One of the things I love about Flatpaks is that they typically don't pollute the home directory, as all their configuration and data files go into their own directory within `~/.var`. I've noticed that with this package, a `~/Unity` directory is created, polluting the home directory. I'd really like to avoid this.

I understand that this package has access to the host filesystem, and Unity Hub wants to create that directory, so it does as it has access. Presumably, taking away access to the host filesystem would break the app in some way as it isn't able to properly handle it?

I feel like I've seen some Flatpak apps though that have access to the host filesystem, while still storing their own things within `~/.var`. Could this package be configured to do the same thing? Wouldn't it just be a matter of the app being told that `~/.var/com.unity.UnityHub/` is its home directory, while still having full filesystem access?

Thanks.

首先检查该软件包的 Flatpak 配置，以及 Unity Hub 如何选择其主目录。确认将应用的主目录迁移到 ~/.var/com.unity.UnityHub/ 下是否仍保留所需的主机文件系统访问权限，然后验证在不破坏应用的情况下不再创建 ~/Unity。

由索引模型根据 Issue 内容生成。