DA: various input issues

[vburckhardt]

• prefix should be in the required tab - not in the optional
• kms related inputs should be on the optional tab - not on the required one
• service_credential_names description should give at least one example on how to input the field as it is a json map.
• related inputs should be grouped together
• cos related description should be more explicit about what the cos instance and bucket is for.
• any input variable name should be prefixed with the context when this is not immediately obvious - eg: archive_days -> cos_bucket_archive_days
• do not use acronyms when this is not obvious - eg: event_notifications and not "en"
• retention_enabled description seems a copy paste from another input description "Set to true to skip the creation of an IAM authorization policy that permits all Event Notifications instances in the resource group to read the encryption key from the KMS instance."
• en_key_name -> review description, it would like make no sense for most end-users. "The name for the key that will be created for the Event Notifications. Not used if an existing key is specfied. If a prefix input variable is specified, it is added to this name in the -value format.". I supposed this is the key protect key and en is event_notification, and that this input is not used if an existing crn key is passed? All of this needs to be explicit in the description.