[JFR] Compilation queue statistics

The current compilation related events don't show whether you are over/under-utilizing your compilation threads; requiring you to experiment with settings to compile as fast as possible (esp in service startup/warmup)

Proposing the following periodic event so that you can determine the pressure on the compilation queues

You will see one event per compiler queue: c1 and c2

The following event definition is in the form used for metadata.xml

  <Event name="CompilerQueueUtilization" category="Java Virtual Machine, Compiler" label="Compiler Queue Utilization" period="everyChunk">
    <Field type="CompilerType" name="compiler" label="Compiler" />
    <Field type="long" contentType="hertz" name="addedRate" label="Requets Added Rate" description="Requests added per second"/>
    <Field type="long" contentType="hertz" name="removedRate" label="Requests Removed Rate" description="Requests removed per second"/>
    <Field type="long" name="queueSize" label="Queue Size"/>
    <Field type="long" name="peakQueueSize" label="Peak Queue Size"/>
    <Field type="long" name="addedCount" label="Requests Added"/>
    <Field type="long" name="removedCount" label="Requests Removed"/>
    <Field type="long" name="totalAddedCount" label="Total Requests Added"/>
    <Field type="long" name="totalRemovedCount" label="Total Requests Removed"/>
    <Field type="int" name="compilerThreadCount" label="Compiler Thread Count"/>
  </Event>

The queues already track the size, tracking peak size and added/removed count is a minor change to the compilerBroker.
Importantly the numberOfThreads should be the current number rather than the configured number for when the dynamic compiler threads option is being used