Summary Metric Support

Is your feature request related to a problem? Please describe.

Add support for Legacy Summary metric type. This metric type is listed as use for legacy systems and not recommended for use in new receivers. That being said a lot of older (legacy) Java JMX systems have metrics that fit the Summary metric model.

Apache HBase is such a system. Particularly the ops metrics:

hbase.regionserver.<op>_<measure>
Operation latencies, where is one of Append, Delete, Mutate, Get, Replay, Increment; and where is one of min, max, mean, median, 75th_percentile, 95th_percentile, 99th_percentile

Describe the solution you'd like
Add support for the summary metric type.

Describe alternatives you've considered
Capture each part of the summary metric as its own metric.

Additional context
I see this was discussed in issue #4075 but after some discussion with @jsuereth we felt it was worth readdressing the need for this. He might be able to more context also.

Start by reading the Legacy Summary metric specification linked in the issue and the prior discussion in issue #4075. Trace how the Java SDK represents and exports metric types, then define the API, compatibility behavior, and tests needed for HBase-style summary metrics; done means supported summary data is covered by tests.