Reorganize Package Structure To Clarify API

[adamgfraser]

The ZIO ZMX library should expose a small number of core abstractions, primarily the Metrics service in the package.scala file, and then specific implementations of that service in appropriate packages (e.g. a statsd implementation in the zio.zmx.stats package). Everything else that is used to implement these services should be package private to provide a clean API for users and flexibility to evolve implementation details.

This ticket is to reorganize the package structure of the project as follows:

• Rename the metrics package to be the statsd package
• Rename UDPClient to StatsdClient and UDPClientUnsafe to StatsdClientUnsafe for clarity since UDP is a communication protocol and this package is really concerned with implementation details that are specific to statsd
• Move the Metrics.live service in the zio.zmx package object to the zio.zmx.statsd package object since this implementation is specific to statsd
• Move the data types in the MetricsDataModel and MetricsConfigDataModel traits to be top level data types within the zio.zmx package and delete the trait. Since the trait is not used anywhere except being extended in the package object this should be the same and will make it easier for users to find these data types.
• Other than the live method in zio.zmx.statsd above make sure everything in any of the zio.zmx sub-packages (e.g. diagnostics, fibers, graph, parser) is private[zmx].

After these changes generating ScalaDoc for ZIO ZMX should produce documentation that only shows the values in the zio.zmx package object, the data types currently in MetricsModel and MetricsDataModel, and the live service in the zio.zmx.statsd package.

[lbdlbdlbdl]

I would like to work on this one.

[adamgfraser]

@lbdlbdlbdl Great!

[atooni]

@lbdlbdlbdl Hello - Are you currently working on this ? - I am asking because it kind of falls in line with the work I am doing to align the prometheus and the statsd API. see #155