RFR: 8340717: Remove unused function declarations from java.c/java.h of the launcher

[Jaikiran Pai]

Can I please get a review of this cleanup to the launcher code to remove declarations of unused functions?

The `ValidateModules` function appears to be a left-over from https://bugs.openjdk.org/browse/JDK-8340717.

The `SetApplicationClassPath` and `PrintMachineDependentOptions` appear to have been unused for a long time (ever since the first commit in the current JDK repo).

The data model related macros, being removed in this PR, are unused and no longer relevant.

No new tests have been added and existing tier1, tier2 and tier3 tests continue to pass with this change.

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Commit messages:
 - 8340717: Remove unused function declarations from java.c/java.h of the launcher

Changes: https://git.openjdk.org/jdk/pull/21149/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21149&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8340717
  Stats: 12 lines in 2 files changed: 0 ins; 12 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/21149.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21149/head:pull/21149

PR: https://git.openjdk.org/jdk/pull/21149