RFR: 8318707: Remove the Java Management Extension (JMX) Management Applet (m-let) feature [v4]

[Kevin Walls]

> Remove the MLet feature and its tests.
> 
> Some tests use MLet classes but are not testing MLets.  These are updated, to use another test MBean or an MBean which is a URLClassLoader, e.g.
> test/jdk/javax/management/MBeanServer/PostExceptionTest.java
> test/jdk/javax/management/remote/mandatory/loading/TargetMBeanTest.java

Kevin Walls has updated the pull request incrementally with one additional commit since the last revision:

  Test update using URLClassLoader MBeans, more like original tests

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Changes:
  - all: https://git.openjdk.org/jdk/pull/16363/files
  - new: https://git.openjdk.org/jdk/pull/16363/files/29ec31f2..70092fa4

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16363&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16363&range=02-03

  Stats: 83 lines in 2 files changed: 68 ins; 1 del; 14 mod
  Patch: https://git.openjdk.org/jdk/pull/16363.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16363/head:pull/16363

PR: https://git.openjdk.org/jdk/pull/16363