feat(stdlib): Add user-friendly file system module

[alex-snezhko]

Add a file system module that is more high-level and user-friendly than the current sys/file

Closes #211

[spotandjake]

The code looks good to me, Most of my comments were related to graindoc.

Two other things:

• Currently the sys/ path is used for more low level wasi interactions. I think we should either move these wasi interactions elsewhere or put this module elsewhere.
• Are we currently able to add some better streaming functions such as File.open, File.readLine and File.close?

[ospencer]

Overall, I love the API design! My major piece of feedback here is that I don't think this module belongs in the sys subdirectory, but in the regular stdlib folder. The sys folder was really just meant for the low-level wasi stuff (and probably should have been named just wasi).

I envision that moving forward to Preview 2, the wasi folder will just have the generated bindings to each of the wasi standards, and we'll have high-level libraries in the regular standard library. We can note in the module doc that use of that library incurs a dependency on a particular wasi world. For now, we can say that use of the module requires WASI Preview 1.

[marcusroberts]

I read all the way through and didn't spot anything, looks like a nice usable interface too.

[spotandjake]

Overall, I love the API design! My major piece of feedback here is that I don't think this module belongs in the sys subdirectory, but in the regular stdlib folder. The sys folder was really just meant for the low-level wasi stuff (and probably should have been named just wasi).

I envision that moving forward to Preview 2, the wasi folder will just have the generated bindings to each of the wasi standards, and we'll have high-level libraries in the regular standard library. We can note in the module doc that use of that library incurs a dependency on a particular wasi world. For now, we can say that use of the module requires WASI Preview 1.

Thoughts on maybe in 0.6 we rename the sys folder to wasi and keep it in the sys subdirectory? I do kind of like the separation especially when considering grain for web development or embedded development where you would not have file system access.