Feature request: Ability to profile any page on demand

Attaching initial patch

Removing a left over comment

I see an issue for similar functionality https://www.drupal.org/project/xhprof/issues/2592489 ✨ Allow to toggel xhprof using a cookie. Needs review
We probably could extend this to work with either query string or storing the secret in cookies to profile every single page, but this could be dangerous, if someone forgets to remove the cookie.

Better to provide both cookie and query-string options

+++ b/src/Form/ConfigForm.php
@@ -47,6 +52,7 @@ class ConfigForm extends ConfigFormBase {
+    $instance->settings = $container->get('settings');

I find it strange to have this in settings singleton, moreover it needs docs and tricky for non-tech users

please use config as other issue with cookie doing, you can always override config value via settings