Identity schema authentication states should match DULE

## What are the schemas that are affected by the issue
Identity

## What are examples of products that are impacted by the issue
all of them that deal with login / CRM ids

## Details
DULE appears to prescribe four _identity states_ to three _authentication states_ that ECID uses and that are being proposed on the identity schema (see https://github.com/adobe/xdm/blob/Add-authentication-states-to-Identity-Schema/schemas/context/identity.schema.json#L35). We should probably go with the DULE states. The DULE states are:

- Not Provided (this should be the default if no other value in the enum is set)
- Identified (corresponds to Authenticated in ECID Auth State?)
- Incognito (corresponds to Logged out in ECID Auth State?)
- Ambiguous (corresponds to Unknown in ECID Auth State?)

Start with schemas/context/identity.schema.json at the linked schema revision, then compare its proposed ECID authentication states with the four DULE identity states listed in the issue. Done means the schema uses the agreed state mapping and defines the appropriate default for an unset value.

Written by the indexing model from the issue text.