- Closes #8808 - adds tests for various scenarios.
- Implements `size` using HEAD.
- Updates existing functions to changes in Cloud API.
- Adds stubs for `*_time` methods, `parent`, `path`.
- [x] TODO: resolve the `Enso_File.current_working_directory` from an environment variable.
- ~~TODO: recursive directory deletion?~~ left for later

# Important Notes
- Currently, the Cloud API does not offer an easy way to extract metadata for a file, in particular to get the parent folder from the file `id`.
- We should be able to get the parent, and stuff like creation/modified time.
- We need a way to resolve paths to asset ids, for `path` to work as well as `current_working_directory`.
- What is the environment variable that will be used to feed the `current_working_directory` property?