[sync] Abstract storage API to access storage

[radumarias]

Have an abstract layer to interact with the filesystem in EncryptedFs. This helps us have several implementations for desktop, WASM, and mobile that handle the particularities of each platform.

Abstractization layer for API similar to https://doc.rust-lang.org/std/fs/struct.File.html , https://doc.rust-lang.org/stable/std/fs/ and https://doc.rust-lang.org/stable/std/io/ and implementation that uses the above ones for accessing local FS. Use that impl in EncryptedFs struct and crypto modules to access FS.

Structure of crypto module

crypto::storage::sync::fs::OpenOptions
crypto::storage::sync::fs::File
crypto::storage::sync::fs
crypto::storage::sync::io
crypto::storage::sync::path::Path](https://doc.rust-lang.org/stable/std/path/struct.Path.html). This is because the existing method uses local fs
crypto::storage::sync::path::PathBuf. This is because the existing method uses local fs

We will have smth similar to how this is atomic Write to a File https://crates.io/crates/atomic-write-file

Flow is like this

lib-users > crypto::[fs, fs::OpenOptions, fs::File, io] > EncryptedFs -> crypto::storage::sync::[fs, fs::OpenOptions, fs::File, io]

This issue corresponds to encrypted_storage::sync::[fs, fs::File, io].

https://github.com/radumarias/rencfs/issues/111