Support multiple buses in fcp

[joajfreitas]

A single fcp schema should be able to describe multiple physical buses.

Syntax proposal for can impls:

Option 1

impl can for Foo {
    id: 10,
    buses: ["bus1", "bus2"],
}

Option 2

impl can for Foo {
    id: 10,
    bus: "bus1"
}

impl can for Foo {
    id: 10,
    bus: "bus2",
}

Open questions

1. How do we handle different IDs for the same message in different buses?

TODO

1. Add support for multiple buses in fcp_dbc
2. Add check in fcp_dbc for conflicts between ids in the same bus.