feat: add opcc slashing event

[parketh]

Summary

This is a PR to update the BTC Slasher program to support and handle OP stack consumer chain slashing events. It accompanies babylonlabs-io/babylon-contract#92.

Test plan

Before running integration tests, I needed to set DOCKER_HOST:

export DOCKER_HOST="unix:///Users/parkyeung/.docker/run/docker.sock"

To run tests:

# unit tests
make test

# integration tests
make test-e2e