RFR: 8347433: Deprecate XML interchange in java.management/javax/management/modelmbean/DescriptorSupport for removal

[Kevin Walls]

DescriptorSupport has a constructor and a method providing creation from, and export to, XML.

This is unused in the JDK and has no practical known examples of usage.  XML parsing is best done by an independent implementation, not this class.

Getting PR out for visibility.  CSR will be added.

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Commit messages:
 - (c)
 - typo
 - Merge remote-tracking branch 'upstream/master' into 8347433_DescriptorSupport_deprecate_XML
 - Also XMLParseException
 - RMMB comment update
 - Deprecate XML interchange in DescriptorSupport

Changes: https://git.openjdk.org/jdk/pull/23038/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23038&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8347433
  Stats: 20 lines in 3 files changed: 13 ins; 3 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/23038.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23038/head:pull/23038

PR: https://git.openjdk.org/jdk/pull/23038