Remove cloud_fliter support?

[Xuanwo]

I'm guessing very few users care about running ofs on windows. Maybe we should just remove it?

[PsiACE]

I need some time to confirm whether there remains a simple approach that works well across different platforms after removal.

Alternatively, we can focus our efforts on one platform until we need to expand.

I find that:

On Windows, JuiceFS relies on WinFsp to mount the file system.