perf(capabilities): Log capabilities providers that are slow

Signed-off-by: Joas Schilling <coding@schilljs.com>

lib/private/CapabilitiesManager.php

@@ -51,7 +51,16 @@ public function getCapabilities(bool $public = false, bool $initialState = false
 						// that we would otherwise inject to every page load
 						continue;
 					}
+					$startTime = microtime(true);
 					$capabilities = array_replace_recursive($capabilities, $c->getCapabilities());
+					$endTime = microtime(true);
+					$duration = $endTime - $startTime;
+					if ($duration > 0.3) {
+						$this->logger->warning('Capabilities of {className} took {duration} seconds to generate.', [
+							'className' => get_class($c),
+							'duration' => round($duration, 2),
+						]);
+					}
 				}
 			} else {
 				throw new \InvalidArgumentException('The given Capability (' . get_class($c) . ') does not implement the ICapability interface');