[code-reflection] Integrated: Onnx proto model test

[Adam Sotona]

Onnx proto model test

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Commit messages:
 - draft of OnnxProtoModelTest::cnnLiftTest
 - OnnxProtoModelTest - work in progress
 - fixed OpGen to avoid CCE
 - reverted OnnxOps change
 - reverted OnnxOps change
 - OnnxProtoModelTest - work in progress
 - OnnxProtoModelTest - work in progress
 - OnnxProtoToModelTest - work in progress
 - Initial work on OnnxProtoToModelTest

Changes: https://git.openjdk.org/babylon/pull/409/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=409&range=00
  Stats: 361 lines in 7 files changed: 332 ins; 9 del; 20 mod
  Patch: https://git.openjdk.org/babylon/pull/409.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/409/head:pull/409

PR: https://git.openjdk.org/babylon/pull/409