Add hook callback for deprecated after_config callback

[djarran]

When installing the plugin on Moodle 4.5, the following error occurs:

Callback after_config in tool_abconfig component should be migrated to new hook callback for core\hook\after_config

    line 7213 of /lib/moodlelib.php: call to debugging()
    line 7280 of /lib/moodlelib.php: call to {closure}()
    line 34 of /lib/classes/hook/after_config.php: call to get_plugins_with_function()
    line 1198 of /lib/setup.php: call to core\hook\after_config->process_legacy_callbacks()
    line 235 of /config.php: call to require_once()
    line 30 of /index.php: call to require_once()

[djarran]

Now that the callback is implemented, it is failing within the hook when creating a new cache when the cache is disabled, such as in the upgrade and install scripts when these two constants are defined:

define('CLI_SCRIPT', true);
define('CACHE_DISABLE_ALL', true);

Error:

root@4ad3d9ae8b15:/var/www/mdl405# XDEBUG_TRIGGER=1 php admin/cli/upgrade.php
!!! Coding error detected, it must be fixed by a programmer: You can only set identifiers on initial definition creation. Define a new cache to set different identifiers. !!!

Debug info:
Error code: codingerror
Stack trace: * line 774 of /cache/classes/definition.php: core\exception\coding_exception thrown
* line 111 of /cache/classes/disabled_factory.php: call to core_cache\definition->set_identifiers()
* line 190 of /cache/classes/cache.php: call to core_cache\disabled_factory->create_cache_from_definition()
* line 263 of /admin/tool/abconfig/classes/experiment_manager.php: call to core_cache\cache::make()
* line 274 of /admin/tool/abconfig/classes/experiment_manager.php: call to tool_abconfig_experiment_manager->get_experiments()
* line 102 of /admin/tool/abconfig/classes/hook_callbacks.php: call to tool_abconfig_experiment_manager->get_active_request()
* line ? of unknownfile: call to tool_abconfig\hook_callbacks::after_config()
* line 318 of /lib/classes/hook/manager.php: call to call_user_func()
* line 1199 of /lib/setup.php: call to core\hook\manager->dispatch()
* line 235 of /config.php: call to require_once()
* line 41 of /admin/cli/upgrade.php: call to require()

This should be caught in the try/catch block in the hook like in Moodle 4.1 but it is getting caught instead the default_exception_handler

    public static function after_config(\core\hook\after_config $hook) {
        try {
            global $SESSION, $USER;

            // Setup experiment manager.
            $manager = new \tool_abconfig_experiment_manager();

            ...
           
        } catch (Exception $e) {        // @codingStandardsIgnoreStart
            // Catch exceptions from stuff not existing during installation process, fail silently
        }                               // @codingStandardsIgnoreEnd
    }

[djarran]

Above issue is resolved - see https://stackoverflow.com/questions/39234250/try-catch-is-ignored-in-moodle-php-when-using-httpful-within-a-class