RFR: 7904049: Add LLM inference example to jextract samples

[Nizar Benalla]

Please review this PR to add an LLM inference example to the jextract samples.

Thanks!

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Commit messages:
 - onnx inference example

Changes: https://git.openjdk.org/jextract/pull/285/files
  Webrev: https://webrevs.openjdk.org/?repo=jextract&pr=285&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7904049
  Stats: 186 lines in 4 files changed: 186 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jextract/pull/285.diff
  Fetch: git fetch https://git.openjdk.org/jextract.git pull/285/head:pull/285

PR: https://git.openjdk.org/jextract/pull/285