[sync] fs, File and io API

[radumarias]

Similar to #97 just for sync API. See if we can leverage it somehow to use the implementation from there.

The structure of crypto module, needs to mimic the std ones:

• crypto::fs_api::sync::fs::OpenOptions
• crypto::fs_api::sync::fs::File
• crypto::fs_api::sync::fs
• crypto::fs_api::sync::io - investigate if we need this
• crypto::fs_api::path::Path - this is because in exists method uses local fs
• [crypto::fs_api::path::PathBuf - this is because in exists method uses local fs

As these are sync methods and our EncryptedFs have async ones, we can use call_async or better channels.