#101 - Do not activate custom-search classes on all page-views

Overview: Civi 5.41 began migrating the "Custom Search" layer to an extension (legacycustomsearches). dataprocessor uses the "Custom Search" layer in an unusual way - which provokes a hard/ubiquitous error during upgrade. This revision makes it more robust against upgrade crashes.

Before: hook_config unconditionally (on all page-views) loads CRM_DataprocessorSearch_Form_Search_Custom_DataprocessorSmartGroupIntegration and calls redirectCustomSearchToDataProcessorSearch($currentUrl).

After: hook_config only calls CRM_DataprocessorSearch_Form_Search_Custom_DataprocessorSmartGroupIntegration if it's needed.

Comments:

• The error arises from when autoloading the base-class CRM_Contact_Form_Search_Custom_Base. This class exists, but it won't be available until the upgrade is complete.
• Strictly speaking, the two conditionals (on $currentUrl and ssID) are sufficient. I threw in a third conditional (class_exists()) as an extra bit of paranoia.
• I did a light r-run to ensure that the upgrade process works with the patch. However, I did not test the redirect.
• We're planning to include a short-term work-around in 5.41.1. However, this work-around will go away soon (eg 5.42 or 5.43).