Clear the state on Chat screen if visitor authentication has changed

[andrews-moc]

Jira issue:
Improve observations for test case #1 from exploratory testing

What was solved?
Since fetch visitor request can receive an error now, Widgets SDK can clear the state on Chat screen if visitor authentication has changed. Otherwise, Chat screen state is invalid.

Release notes:

• Feature
• Ignore
• Release notes (Is it clear from the description here?)
• Migration guide (If changes are needed for integrator already using the SDK - what needs to be communicated? Add underneath please)

Additional info:

• Is the feature sufficiently tested? All tests fixed? Necessary unit, acceptance, snapshots added? Check that at least new public classes & methods are covered with unit tests
• Did you add logging beneficial for troubleshooting of customer issues?
• Did you add new logging? We would like the logging between platforms to be similar. Refer to Logging from Android SDKs → Things to consider for newly added logs in Confluence for more information.

[Pelkar]

LGTM