[web-db] implement clearing sensitive data

Summary: Initial version of hook responsible for handling sensitive data.

Test Plan:
Tested on both web and desktop

1. Make sure the user is logged out and there is no opened app
   • IndexedDB storage should be empty

• And view shared workers (in Chrome it's URL chrome://inspect/#workers) and there shouldn't be anything connected to localhost.

2. Log in
   • console should log Database initialization success
   • check indexedDB content

• see if worker was spawned

1. • see Worker logs (it's separate console)
   • it should say Creating fresh database - Db version: 0
2. Close the tab
   • worker should die (not listed)
3. Open the tab
   • console should log Database initialization success
   • see if worker was spawned
   • see Worker logs - it should say Database exists and is properly encrypted, using persisted data
   • Log out
   • IndexedDB content should be deleted
   • worker is alive until tab is opened

Reviewers: michal, tomek, marcin

Reviewed By: tomek, marcin

Subscribers: ashoat, atul

Differential Revision: https://phab.comm.dev/D7191