feat: replace TokenSent event with CrossSubnetMessageSent

[sebastiendan]

Description

With the messaging features of ToposCore now extracted into a new ToposMessaging contract, the current logic for the sequencer process to capture events linked to cross-subnet messages must be updated.

This PR updates the sequencer so that it consumes new CrossSubnetMessageSent events emitted by ToposCore.

Additions and Changes

• Update ToposCore ABI
• Replace the decoding of TokenSent events by the one of CrossSubnetMessageSent events
• Update the decoding to solely decode the targetSubnetId field (other fields weren't used beforehand anyway)

PR Checklist:

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added or updated tests that comprehensively prove my change is effective or that my feature works

[sebastiendan]

@topos-network/protocol This is a suggestion of update, I will let you confirm whether it's enough or whether we want a better version of it