New metrics are necessary because the new API no longer wraps
an EPP flow, therefore does not get metrics for free.
Metrics include
- An EventMetric for processing time
- An IncrementableMetric for request count, with
availability (available/reserved/registered) and
pricing (standard/premium) fields
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=199708592
