Disallow hyphens from metric names/namespaces

[asanderson15]

No description provided.

[carterkozak]

We could switch from banning underscore to banning hyphen, and update all consumers. Prometheus has a similar constraint and renames hyphens to underscores, but we found it was more common to define metrics in code using hyphens than underscores.

By producing metrics from a schema we can also produce documentation tailored specifically toward the normalized format we send to a collector so it may not be necessary to modify the inputs at all. I'd like to take it a step farther and build validation based on the schema so we don't need to worry about getting these things slightly wrong, the robots should be able to validate pre-merge.