[native] don't generate or send one time keys on login

Summary:
don't call getOneTimeKeys anymore during identity login. also updated the relevant C++ and Rust code to not expect one-time keys

Depends on D11363

Test Plan: logged in from native and confirmed that no new one time keys were added to ddb

Reviewers: bartek, kamil, marcin, ashoat

Reviewed By: bartek, ashoat

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D11364