[code-reflection] RFR: OnnxLift prototype

[Adam Sotona]

This is a prototype of OnnxLift tool.
It lifts ONNX model binary to ONNX code reflection model, extracts weights, and generates Java model source.

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Commit messages:
 - OnnxLift prototype

Changes: https://git.openjdk.org/babylon/pull/638/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=638&range=00
  Stats: 729 lines in 3 files changed: 727 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/babylon/pull/638.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/638/head:pull/638

PR: https://git.openjdk.org/babylon/pull/638