Adding Dispute Participation Metrics (#6838)

* Added participation and queue sizes metrics

* First draft of all metric code

* Tests pass

* Changed Metrics to field on participation + queues

* fmt

* Improving naming

* Refactor, placing timer in ParticipationRequest

* fmt

* Final cleanup

* Revert "Final cleanup"

This reverts commit 02e5608df64b2e0f7810905e4508673b2037d351.

* Changing metric names

* Implementing Eq only for unit tests

* fmt