fix: adjust messaging messages status + add testing feature

[glihm]

This PR had two objectives:

1. Fixing some computation around messaging that were wrong. Also, the status of the messages to app chain is now clearer and directly stored in the storage instead of relying on a magic value.
2. Adding to piltover a functionality to be tested without relying on the proof. By adding a function to register the messages hashes, this ease the local testing, exampled for Katana here.

The new functionality to test the messaging is gated under the messaging_test feature. Which should be ignored for code being built in production.

[glihm]

About the bindings, may be better to have a /bin that we can call to generate the bindings + check if they are up to date.

Then having a /lib to be imported by other projects without them having to rebuild it.

WDYT?