RFR: 8312125: Refactor CDS enum class handling

[Ioi Lam]

Please review this simple refactoring of the CDS code for handling enum classes. The code is moved to new files cdsEnumKlass.cpp/hpp. There's otherwise no change.

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Commit messages:
 - 8312125: Refactor CDS enum class handling

Changes: https://git.openjdk.org/jdk/pull/20013/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20013&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8312125
  Stats: 285 lines in 5 files changed: 190 ins; 93 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/20013.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20013/head:pull/20013

PR: https://git.openjdk.org/jdk/pull/20013