Update references from extension aliases to the CRM_Core_Extension

[eileenmcnaughton]

Prior to CiviCRM 5.52 we threw a mismash of these extensions. They all had to work everywhere because it was unpredictable. In 5.52 we made the API_Exception and CiviCRM_Api3_Exception aliases of CRM_Core_Exception. However, on the off chance people are creating extensions for really old civi versions with the latest civix it would still be handled on those older versions (we were always throwing CRM_Core_Exception all over the show)

[totten]

Yeah, I think this works. 👍

The templates affected here are like demonstrative code (some soft @throws and some illustrations of "how you might use an exception") rather than "central glue affecting all handling of exception". Even if there are some existing extensions/historical versions which treat API_Exception and CRM_Core_Exception differently... it doesn't really affect the quality of the demonstration.