[web] olmAPI on shared worker

Summary:
ENG-6768 : Migrate validateAndUploadPreKeys to shared worker
ENG-6658 : Migrate encrypt, decrypt to shared worker
Part of ENG-6657 : Migrate session creation code to shared worker

Using a similar approach as in D11275 (one message type for calling the methods) this diff moves the olmAPI to the shared worker. There are two logic changes which I have annotated in inline comments. Other than that the only changes are related to using real persisting functions and not the mocked ones in olm-api.js (which are now removed). In this case the olmAPI proxied functions are not hidden behind a flag as they were using mock functions anyway.

Depends on D11326

Test Plan: Called each of the methods and checked if they work. The encrypt/decrypt/contentInboundSessionCreator have been tested in context of peer to peer message communication.

Reviewers: kamil, tomek

Reviewed By: kamil

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D11338