[web] Keep activeChatThreadID and pendingThread updated in navInfo in thread creation mode

Summary:
The diff introduces updating activeChatThreadID and pendingThread in navInfo in thread creation mode.
These values from navInfo are not used by chat-message-list-container when creating thread, but can be read from different places of the app - e.g. by ThreadListProvider.
After the change, thread currently being created (or selected from existing by matching users) is correctly displayed in the thread list on the left, and after clicking on the thread on list, the creation mode is closed and pending thread is correctly being displayed.

Test Plan:
Selecting some new set of users in thread creation mode to display pending thread. It should be correclty displayed on the top of the thread list.
After clicking on the thread, creation mode should be closed and pending thread should remain open (even after page refresh)

Reviewers: tomek, atul, abosh

Reviewed By: tomek

Subscribers: ashoat, adrian, abosh

Differential Revision: https://phab.comm.dev/D4474