Remove legacy duplicate metric classes in helix-core

[narendly]

Issues

• My PR addresses the following Helix issues and references them in the PR description:

Fixes #1146

Description

• Here are some details about my PR, including screenshots of any UI changes:

As part of ZooKeeper API separation initiative, most metric-related classes were moved to metrics-common module. However, there were some that were left in helix-core for backward-compatibility purposes, but these were causing class conflicts at runtime. This change removes such classes.

Tests

• The following tests are written for this issue:

No tests written.

• The following is the result of the "mvn test" command on the appropriate module:

zookeeper-api:

[INFO] Tests run: 37, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 51.075 s - in TestSuite
[INFO] 
[INFO] Results:
[INFO] 
[INFO] Tests run: 37, Failures: 0, Errors: 0, Skipped: 0
[INFO] 
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  54.857 s
[INFO] Finished at: 2020-07-13T21:24:50-07:00
[INFO] ------------------------------------------------------------------------

helix-core:

[INFO] Results:
[INFO] 
[ERROR] Failures: 
[ERROR]   TestEnableCompression.testEnableCompressionResource:117 expected:<true> but was:<false>
[ERROR]   TestControllerLeadershipChange.testMissingTopStateDurationMonitoring:262 expected:<true> but was:<false>
[ERROR]   TestRebalanceRunningTask.testFixedTargetTaskAndEnabledRebalanceAndNodeAdded:330 expected:<true> but was:<false>
[INFO] 
[ERROR] Tests run: 1152, Failures: 3, Errors: 0, Skipped: 0
[INFO] 
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE

Failures were ran individually:

[INFO] Tests run: 10, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 50.368 s - in TestSuite
[INFO] 
[INFO] Results:
[INFO] 
[INFO] Tests run: 10, Failures: 0, Errors: 0, Skipped: 0
[INFO] 
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS

Commits

• My commits all reference appropriate Apache Helix GitHub issues in their subject lines. In addition, my commits follow the guidelines from "How to write a good git commit message":
  1. Subject is separated from body by a blank line
  2. Subject is limited to 50 characters (not including Jira issue reference)
  3. Subject does not end with a period
  4. Subject uses the imperative mood ("add", not "adding")
  5. Body wraps at 72 characters
  6. Body explains "what" and "why", not "how"

Code Quality

• My diff has been formatted using helix-style.xml
  (helix-style-intellij.xml if IntelliJ IDE is used)

[narendly]

@pkuwm It seems that you submitted a change to DynamicMBeanProvider.java recently. Could you give this a quick look and make sure your change wasn't overriden?