Add tracking of the number of brillig VM steps to run example programs to CI

[TomAFrench]

@vezenovm added tracking of the number of steps the brillig VM takes to execute in order #6327. We've now got a number of PRs which look to improve brillig execution speed at the expense of bytecode size (e.g. #6332) so it would be good to have quantifiable numbers on how much these improve execution.

We can reuse the same gates-report github action in order to track the number of opcodes executed to see how these PRs affect it.