Stop recommending using \Drupal\Component\Assertion\Handle::register() in example.settings.local.php

Looks great. The rest of that issue is tricky, but this feels like something to get in as soon as possible to minimise the number of installs using the class.

I'm surprised the docblock above this doesn't need an update. I checked what it says:

/**                                                                             
 * Assertions.                                                                  
 *                                                                              
 * The Drupal project primarily uses runtime assertions to enforce the          
 * expectations of the API by failing when incorrect calls are made by code     
 * under development.                                                           
 *                                                                              
 * @see http://php.net/assert                                                   
 * @see https://www.drupal.org/node/2492225                                     
 *                                                                              
 * If you are using PHP 7.0 it is strongly recommended that you set             
 * zend.assertions=1 in the PHP.ini file (It cannot be changed from .htaccess   
 * or runtime) on development machines and to 0 in production.                  
 *                                                                              
 * @see https://wiki.php.net/rfc/expectations                                   
 */

Some of that is out of date, but not in a way that pertains to the code.

Adding some credits from the other issue.

Committed to 10.1.x and cherry-picked to 10.0.x and 9.5.x.

I wasn't sure about backporting this to 9.4.x. Since it changes default patterns for site-owner managed files (in this case, local.settings.php we have to explain the addition/change in a release note). The backport wouldn't affect existing sites -- only new or reinstalled ones that copy over the new example.settings.local.php -- so in that sense it's non-disruptive.

I think it's probably okay to backport; we would just need the release note a little sooner then (and to adjust the issue tags accordingly).

Leaving at PTBP to discuss one way or another and to add the release note (which is needed either way).

Seems this didn't make it to 9.5.x.

I am not sure this is worth the backport to 9.4.x, it's hardly critical and we don't usually make these kinds of changes in patch releases.

Must've had a failed push.

Added a release note.