Oxidize `UserStorage`

[FirelightFlagboy]

UserStorage depends on ManifestStorage so to simplify the migration. I suggest we first migrate ManifestStorage (tracked in #3169) then migrate UserStorage

TODOs

• [ ] Remove the dependency on the python class ManifestStorage (the class in implemented in Rust but not binded see #3169)
• [ ] Replace the python class UserStorage with the Rust one using pyo3
• [ ] Correct the fixture initialize_local_user_manifest at tests/fixtures.py
• [ ] Correct the fixture initialize_local_user_manifest at tests/common/binder.py
• [ ] Correct the fixture alice_user_storage at tests/core/fs/storage/test_user_storage.py
• [ ] Correct the test test_initialization at tests/core/fs/storage/test_user_storage.py
• [ ] Correct the test test_storage_file_tree at tests/core/fs/storage/test_user_storage.py