support micrometer

[pjfanning]

zio-metrics supports some of the most commonly used metrics standards (prometheus, dropwizard, statsd) but micrometer supports these and more.

Would there be any interest in having an additional zio-metrics-micrometer module where as part of the ZIO Environment, the user would provide a micrometer registry that binds the micrometer metrics to a particular backend. https://micrometer.io/docs has a list of some of the backends that are supported.

Using the existing zio-metrics-prometheus code as a guide, it should be relatively straightforward to produce a micrometer equivalent.

[pjfanning]

I have an experimental micrometer based implementation at https://github.com/pjfanning/zio-metrics-micrometer