[protos] Replace challengeResponse with nonce and signature pair
Summary:
Addresses option 3 from ENG-7641.
Replaced challenge_response with separate nonce and nonce_signature fields.
Updated all usages
Depends on D11549
Test Plan:
- Everything compiles
- Updated unit and integration tests
- Tested QR Auth on native and web
Reviewers: ashoat, varun
Reviewed By: ashoat, varun
Subscribers: tomek
Differential Revision: https://phab.comm.dev/D11551