[lib] refactor processing updates and setting urlPrefix in keyserver-reducer to ops

Summary:
Convert logic to ops approach.

Depends on D10763

Test Plan:
Test for processUpdatesActionType:

1. Open native app
2. Open web app with the same account
3. Make some actions on web account
4. Make sure updatesCurrentAsOf is properly set on native

Test for setURLPrefix:

1. On native in dev-tools select different url

Test for updateLastCommunicatedPlatformDetailsActionType

1. Make shouldSendPlatformDetails: true
2. Verify is state is properly set

Reviewers: inka

Reviewed By: inka

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D10766