glightning: update listpeers test

shutdown subscription

Introduces structs for connection and disconnection notifications
ensuring compatibility with cln v24.11 and onward. Preserves
existing fields for backward compatibility with earlier versions.

plugin: version up with backward compatibility for connection

add DiscountVirtualSize field to Tx struct

elementsd: add DiscountVirtualSize

- Add DecodeRequest and DecodeResult structs for the new 'decode' command
- Implement Decode() method that uses the new RPC command
- Update DecodeBolt11() to use 'decode' with fallback to 'decodepay'
- Mark DecodePay() as deprecated
- Add DecodeRequest to RPC method map

The 'decodepay' command was deprecated in Core Lightning v24.11 in favor
of the more general 'decode' command. This change maintains backward
compatibility while supporting the new command.

Fixes compatibility with Core Lightning v24.11+

Add support for new 'decode' RPC command