[R][Documentation] Create documentation for undocumented methods and args in filesystem.R

[amoeba]

Describe the bug, including details regarding any error messages, version, and platform.

The manual page for ?FileSystem is missing some methods such as $ls() so it would be good to go over that page to document anything that's missing. We don't use roxygen2's R6 functionality due to reasons outlined in #23127 which is why it's possible for the docs for R6 classes to get out of sync. This also means other R6 classes in other files may need a review once filesystem.R is updated.

Component(s)

Documentation, R

[amoeba]

take

[amoeba]

I looked at all of the R6 classes in filesystem.R and looked for missing docs in methods, active bindings, and $create functions. I found:

• S3FileSystem$create is missing a docstring for proxy_options
• GcsFileSystem was missing docs for the active binding options , which I missed in [R] Expose GcsFileSystem options in R #34422
• FileSystem was missing docs for methods path, cd, and ls

Edit: I opted not to document clone and print since they're inherited but would document them if nudged.