Try to get rid of max body size limitation

[gzurl]

From @ereslibre at #22 (HTTP Request Body to WASI stdin):

I think we could get rid of the max body limitation if we follow mod_cgi's approach.

They call to cgi_handle_request. It reads the request body and writes it to a file descriptor. We could use this file descriptor to pass the body of the request to wasi_stdin instead of building an ad-hoc pipe.

I think it would be feasible, but haven't checked it.

I believe it could be worth it to take a look at this.

[scothis]

I haven't found a good fake for the manager and builder resources that would make them unit testable. e2e testing is the preferred approach to date.

It might be worth dealing with the complexity of creating our own fakes since this is a significant part of the controller that isn't unit testable today.