RFR: 8296754: AutoCreateSharedArchive in JDK 20 is not compatible with JDK 19

[Matias Saavedra Silva]

The -XX:+AutoCreateSharedArchive flag was implemented in JDK 19, however, this flag doesn't work across JDK 19 and 20.

Expected: JDK 20 should recreate the specified CDS archive
Actual: JDK 20 cannot recognize the archive file and gives up

The new field from GenericCDSFileMapHeader is now in FileMapHeader.

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Commit messages:
 - Adjusted whitespace
 - Added test
 - 8296754: AutoCreateSharedArchive in JDK 20 is not compatible with JDK 19

Changes: https://git.openjdk.org/jdk/pull/11148/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11148&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8296754
  Stats: 252 lines in 7 files changed: 196 ins; 16 del; 40 mod
  Patch: https://git.openjdk.org/jdk/pull/11148.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11148/head:pull/11148

PR: https://git.openjdk.org/jdk/pull/11148