[crypto] unify key types and introduce type for Inbound Keys

Summary:

1. Move some types from CommCoreModuleSchema.js -> crypto-types.js
2. Add validator for SignedPrekeys
3. UserDevicesOlmInboundKeys type and validator
4. Group types in identity-service-types.js

Test Plan: FLow

Reviewers: marcin, varun, tomek

Reviewed By: tomek

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D11106