RFR: CODETOOLS-7902867: JOL: Use defined data model to print the header in class layout

[Aleksey Shipilev]

JOLSample_10_DataModels does not work properly after CODETOOLS-7902866. It only takes care of the "actual" VM layout, ignoring the defined data model. We need to make ClassLayout accept the data model.

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Commit messages:
 - Remove excess imports
 - Remodel data model

Changes: https://git.openjdk.java.net/jol/pull/12/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jol&pr=12&range=00
  Issue: https://bugs.openjdk.java.net/browse/CODETOOLS-7902867
  Stats: 974 lines in 20 files changed: 573 ins; 340 del; 61 mod
  Patch: https://git.openjdk.java.net/jol/pull/12.diff
  Fetch: git fetch https://git.openjdk.java.net/jol pull/12/head:pull/12

PR: https://git.openjdk.java.net/jol/pull/12