RFR: 8306055: Add a built-in Catalog to JDK XML module

[Joe Wang]

Implement the built-in Catalog.

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Commit messages:
 - fix whitespace error
 - 8306055: Add a built-in Catalog to JDK XML module

Changes: https://git.openjdk.org/jdk/pull/16719/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16719&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8306055
  Stats: 1641 lines in 50 files changed: 1429 ins; 118 del; 94 mod
  Patch: https://git.openjdk.org/jdk/pull/16719.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16719/head:pull/16719

PR: https://git.openjdk.org/jdk/pull/16719