Incoming handler virtualization

[guybedford]

@dicej did some exploration here on what would be involved in dicej@99d950f.

This currently hits limitations with wasm-compose due to a cyclical case, which would need to be acyclified via a wrapper adapter module with a table.

There are new WIT techniques being planned here which should resolve these issues though more generally. In addition cycle fixes for wasm-compose should also be able to unblock progress here.

In addition the approach above should be able to combine with component rewriting to form a proper wrapper virt for HTTP incoming requests.

Joel please correct me where I'm wrong and feel free to fill in some more background on this as well.