Support specifying standard and extension-specific middleware.
Extensions recently gained support for loading additional middleware,

and I recently updated it to require that the middleware take an

extension parameter in the constructor. However, this makes it harder to

use middleware provided by third-parties that aren't extension-aware.
Now, we introspect the middleware's constructor and see if it's

extension-aware or not. We can then initialize it appropriately.

Tested this with an extension that had extension-aware middleware, and

tested it with another extension that used standard middleware from

a different project, and both initialized fine.