Provide message router handler

[julienrbrt]

Some modules require a message router handler (e.g gov or authz)
We need to make sure depinject can provide a stf compatible message router handler to such modules.
Additionally, we need a helper for those manually wiring those modules.

• Introduce core router service
• Implement router service in runtime
• Implement router service in runtime/v2
• Wire in x/gov
• Wire in x/authz
• Wire in x/group

[tac0turtle]

should we provide routers through env?

[julienrbrt]

should we provide routers through env?

I don't think we should. If we ever want to move away from module being super user, we should not let any module be easily able to execute anything.

[tac0turtle]

Whatever router is passed we should require the caller to be set