[code-reflection] RFR: ONNX fixes [v2]

[Adam Sotona]

> This patch includes:
> - `OnnxTransformer` fix of returning in-code constructed list of tensors
> - `README.md` fix of the examples execution
> - workaround to avoid CNFE when the `ReleaseEnv` class is attempted to load in the above shutdown hook from already closed classloader

Adam Sotona has updated the pull request incrementally with one additional commit since the last revision:

  CNFE workaround moved to static initializer

-------------

Changes:
  - all: https://git.openjdk.org/babylon/pull/565/files
  - new: https://git.openjdk.org/babylon/pull/565/files/1fd921f2..6877c7b8

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=babylon&pr=565&range=01
 - incr: https://webrevs.openjdk.org/?repo=babylon&pr=565&range=00-01

  Stats: 10 lines in 1 file changed: 6 ins; 4 del; 0 mod
  Patch: https://git.openjdk.org/babylon/pull/565.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/565/head:pull/565

PR: https://git.openjdk.org/babylon/pull/565