(POOLER-160) Revise Metrics Classwork

Review changes suggested to revise the Metrics related files into a more
logical class structure.

Also fixup grammar typos in docs strings and any trailing metrics that
have been recently added to vmpooler.

lib/vmpooler/metrics.rb

@@ -1,24 +1,24 @@
 # frozen_string_literal: true
 
+require 'vmpooler/metrics/statsd'
+require 'vmpooler/metrics/graphite'
+require 'vmpooler/metrics/promstats'
+require 'vmpooler/metrics/dummy_statsd'
+
 module Vmpooler
   class Metrics
     # static class instantiate appropriate metrics object.
     def self.init(logger, params)
       if params[:statsd]
-        metrics = Vmpooler::Statsd.new(logger, params[:statsd])
+        metrics = Vmpooler::Metrics::Statsd.new(logger, params[:statsd])
       elsif params[:graphite]
-        metrics = Vmpooler::Graphite.new(logger, params[:graphite])
+        metrics = Vmpooler::Metrics::Graphite.new(logger, params[:graphite])
       elsif params[:prometheus]
-        metrics = Vmpooler::Promstats.new(logger, params[:prometheus])
+        metrics = Vmpooler::Metrics::Promstats.new(logger, params[:prometheus])
       else
-        metrics = Vmpooler::DummyStatsd.new
+        metrics = Vmpooler::Metrics::DummyStatsd.new
       end
       metrics
     end
   end
 end
-
-require 'vmpooler/metrics/statsd'
-require 'vmpooler/metrics/dummy_statsd'
-require 'vmpooler/metrics/graphite'
-require 'vmpooler/metrics/promstats'