[CommRustModule] improve error handling

Summary:
Handle message form Identity and upload one-time keys on demand.

Addresses https://phab.comm.dev/D10374#inline-63986

Test Plan:

1. Add throw std::runtime_error("TEST ERRROR"); in one of methods
2. Call method
3. Verify that promise is rejected

Reviewers: marcin, varun, michal

Reviewed By: marcin, varun

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D10530