Implement utilities and database query wrapper to create new olm session on eht keyserver side

Summary: This differential implements relevant olm utils and creator to create olm session for particular cookie id with initial encrypted message provided by the client.

Test Plan:
Modify keyserver codebase so that it prints: prekey, one time keys and notifications identity keys to the console. Use provided keys to initialize olm session on the client side and generate initial encrypted message. Call olm-session-creator with hardcoded initial encrypted
message in logInResponder (so that we have valid cookie to use). Examine database content using preferred tool of choice. there should be an entry with pickled olm session.

Reviewers: tomek, atul, bartek, ashoat

Reviewed By: ashoat

Subscribers: anunay, ashoat

Differential Revision: https://phab.comm.dev/D7631