Improvements in Audit Log for "Impersonating a user"

We don't have enough logging in place when an org admin impersonates / logs in as another user. 

Below are the areas of improvement:

• When an admin logs out as another user then this is not audited or logged in the audit logs. 
• Having a tag (impersonated by <admin>) in the product logs when product configurations are updated
• We should have logs to track activities performed by the admin who impersonated another user.