Implement filter method on check collection.

includes/Checker/Default_Check_Collection.php

@@ -67,6 +67,24 @@ public function to_map(): array {
 		return $this->checks;
 	}
 
+	/**
+	 * Returns a new check collection containing the subset of checks based on the given check filter function.
+	 *
+	 * @since n.e.x.t
+	 *
+	 * @param callable $filter_fn Filter function that accepts a single check object and should return a boolean for
+	 *                            whether to include the check in the new collection.
+	 * @return Check_Collection New check collection, effectively a subset of this one.
+	 */
+	public function filter( callable $filter_fn ): Check_Collection {
+		return new self(
+			array_filter(
+				$this->checks,
+				$filter_fn
+			)
+		);
+	}
+
 	/**
 	 * Returns a new check collection containing the subset of checks based on the given check slugs.
 	 *

includes/Checker/Default_Check_Repository.php

@@ -102,13 +102,10 @@ public function get_checks( $flags = self::TYPE_ALL ) {
 		}
 
 		// Remove experimental checks before returning.
-		return new Default_Check_Collection(
-			array_filter(
-				$checks,
-				static function ( $check ) {
-					return $check->get_stability() !== Check::STABILITY_EXPERIMENTAL;
-				}
-			)
+		return ( new Default_Check_Collection( $checks ) )->filter(
+			static function ( $check ) {
+				return $check->get_stability() !== Check::STABILITY_EXPERIMENTAL;
+			}
 		);
 	}
 }