RFR: 8306310: Move is_shared Klass flag

[Coleen Phillimore]

Please review this simple patch to move the is_shared_class flag to Klass, CDS flags.  The eventual goal is to have AccessFlags only be ones defined in the classfile.
Tested with tier1-4.

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Commit messages:
 - 8306310: Move is_shared Klass flag

Changes: https://git.openjdk.org/jdk/pull/13514/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13514&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8306310
  Stats: 15 lines in 2 files changed: 10 ins; 5 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/13514.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13514/head:pull/13514

PR: https://git.openjdk.org/jdk/pull/13514