[keyserver/ web] Handle device_token on web

Summary: We need to store device_token on web so we can save push service endpoints and auth info. This diff make deviceToken a proper field in web redux and enables the web app to set it's device token on keyserver. I've removed isDeviceType checks in places where previously we skipped handling deviceToken for the web platform.

Test Plan:
Tested with the next diffs in stack that set the device_token:

• check that the device_token is correctly set in the database and in the redux on web
• check that after logging out the device_token is assigned to an anonymous cookie
• check that after another user logs in they get the device's device_token

Reviewers: tomek, atul, kamil, inka, ashoat

Reviewed By: tomek, inka, ashoat

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D6815