Export Metrics

[Stebalien]

We need to get timing metrics from StateManager.ApplyBlocks. They're recorded using our standard metrics system, but we need a way to extract and write them to disk.

[Stebalien]

Ok. I'd actually like this to get done eventually, but it's not a high priority.

Specifically, I'd like to periodically, randomly, record timing metrics to disk. Motivations include:

1. Ability to pipeline/optimize the simulation when not timing.
2. Ability to "trim" the chain without losing information around timing changes.

[BigLep]

Removing from the Hyperdrive milestone since not essential for a quality 0.10 release.