RFR: 8344969: Remove the jmx.mxbean.multiname compatibility property

[Kevin Walls]

Remove the System Property "jmx.mxbean.multiname" which was introduced in JDK-7 for compatibility with code which may have depended on previous incorrect behaviour.  Removal is long overdue.

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Commit messages:
 - 8344969: Remove the jmx.mxbean.multiname compatibility property

Changes: https://git.openjdk.org/jdk/pull/23131/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23131&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8344969
  Stats: 9 lines in 2 files changed: 0 ins; 5 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/23131.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23131/head:pull/23131

PR: https://git.openjdk.org/jdk/pull/23131