We define a new subtype 'modern_scb_chan' and a new tlvtype 'scb_tlvs' which includes
all the relevant information to create a penalty transaction when the peer tries to cheat.
Key Changes:
- Rename the old format to 'legacy_scb_chan' and define a new type 'modern_scb_chan'
- Include TLVs to 'modern_scb_chan'
- Create a new msgtype 'static_chan_backup_with_tlvs'
- Modify 'struct channel' to include 'struct modern_scb_chan'
- Add these two types to 'varsize_types' in generate.py
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