Fix issue with cached browse config not being removed

[Colengms]

We cache the last used browse config, to avoid resetting the contents of the database on the next session while waiting for the same config provider to register again.

For security purposes, we want to clear that cached browse config if the same provider does not register in a subsequent session. Clearing the browse configuration at the end of the session is not reliable, as the call to update on the Momento is async, and may not complete.

With this change, we now persist the providers that have registered in a workspace folder, and, on a subsequent session, if we see that the provider of the cached browse configuration did not register in the previous session, the cached browse config removed.

Moved the persistent variables involved into the client object.