Storage-bucket

Remove the callable classes. After we stopped using `returns` they weren't really doing anything. Removing this also removes about half the codebase and makes developing new features easier.

Breaking

* The Callable class `GetClient` is removed.
* The Callable class `GetBucket` is removed.
* The Callable class `CreateBucket` is removed.
* The Callable class `DeleteBucket` is removed.
* The Callable class `DeleteFile` is removed.
* The Callable class `DownloadFile` is removed.
* The Callable class `ListBuckets` is removed.
* The Callable class `ListFiles` is removed.
* The Callable class `UploadFile` is removed.

Features

* Can now import directly from `storage_bucket`. Before: `from storage_bucket.download_file import download_file` -> `from storage_bucket import download_file`


Docs

* Examples in docs now import functions directly from `storage_bucket`
* Removes anything related to returns from docs (48)[https://github.com/thomasborgen/storage-bucket/issues/48]

This change has been on my mind a while. Using Returns library and especially wanting to use its latest releases creates a dependency hell since every release is breaking. We don't really need it so until its mature enough, lets stop using it.

Breaking changes

* Remove `returns` dependency
* One can no longer use `.map`, `.bind`, `.failure` etc after calling the Callable objects like `DeleteFile()().bind(...)`.
* Instead use the normal snake_case functions like: `delete_file()`

Fixes

* Test workflows in github are now working again after some key changes.