jmx-dev RFR: 8344966: Remove the allowNonPublic MBean compatibility property

[Kevin Walls]

The System Property "jdk.jmx.mbeans.allowNonPublic" was added with JDK-8010285, to optionally be compatible with a time before JDK-8, when Management Interfaces being public was not enforced.

>From JDK-8010285:
_The system property "jdk.jmx.mbeans.allowNonPublic" is used to revert to the old behaviour allowing non-public management interfaces. This property is considered to be transitional and will be removed in the subsequent releases._



That was a long time ago.  This compatibility convenience flag should be removed.

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Commit messages:
 - 8344966: Remove the allowNonPublic MBean compatibility property

Changes: https://git.openjdk.org/jdk/pull/23098/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23098&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8344966
  Stats: 289 lines in 6 files changed: 0 ins; 283 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/23098.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23098/head:pull/23098

PR: https://git.openjdk.org/jdk/pull/23098