Move logic out of Swagger::__construct()

[cnizzardini]

See notes from #453

Even when hotReload is disabled a full controller and model scan is performed + any userland events will fire. Attempt backporting to 2.x.

If you have expensive event listeners you can do a work around like this:

public function schemaCreated(Event $event): void
{
    if (PHP_SAPI === 'cli' || Configure::read('SwaggerBake.hotReload')) {
        // event will only run in CLI or when hot reload is enabled
    }
}

For expensive controller & model scans there is no workaround.

[cnizzardini]

There will be no backport to 2.x, this has been resolved in the yet-to-be-released v3.0.0.