[keyserver] modify createPickledOlmSession

Summary: if the other party's curve25519 olm identity key and one-time key are available, call create_inbound_from instead of create_inbound

Test Plan: tested in subsequent diff

Reviewers: marcin, ashoat

Reviewed By: marcin, ashoat

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D8929