POC: MetricPlugins

[coleaeason]

Details

Implements first class support for a Metric Plugin in Bedrock. The metric plugin can be extended to support any arbitrary implementation of a metric sender or provider (statsd, telegraf, prometheus, etc). An example statsd provider is included but I plan to remove it and move it to a stand alone repo.

@tylerkaraszewski can you please review and give your thoughts? I don't love the global metric function but I am not sure what better option there is to implement this to allow it to add metrics from the whole stack. Attaching the metric recorder to the server allows plugins to also queue their own metrics.

Leaving this as WIP for now until we agree at least on the rough design.

Fixed Issues

Fixes GH_LINK

Tests

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Internal Testing Reminder: when changing bedrock, please compile auth against your new changes

[melvin-bot]

I see this code uses list. If your primary use case is just checking to see if an item exists in the list, perhaps set is a better choice, as it's much faster for random access. C++ has a variety of data structures available to choose from, so pick the best for your use case.