Demo: TX Kernel is able to consume messages from the shared inbox

Currently, the TX Kernel assumes a unique inbox per rollup. This is no longer the case

Therefore, the TX Kernel must be able to distinguish messages from the shared inbox that are meant for it, and to process them. Messages for other rollups should be ignored

1. An encoding exists for the shared inbox 'framing protocol'
2. The TX Kernel is updated to make use of the shared inbox (blocked by #4140 (closed))

Sub-tasks for this:

• Internal message is now a variant with: [Transfer; SOL; EOL; (soon Info_per_level)]
• Internel transfer has a new field destination
• Consider internal transfers where destination = kernel.address, needs #4140 (closed)