[lib] Add types for Blob Service requests and responses

Summary:
Added types and validators for Blob service batch-holder endpoints.
They directly correspond to Rust structs from D13617.

Depends on D13654

Test Plan: flow. Their usage is tested in the next diff

Reviewers: kamil, tomek

Reviewed By: kamil

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D13655