[code-reflection] RFR: OnnxRuntime and OnnxProtoBuilder continuation [v5]

[Adam Sotona]

> OnnxRuntime and OnnxProtoBuilder continuation

Adam Sotona has updated the pull request incrementally with two additional commits since the last revision:

 - initial implementation of optional inputs
   
 - removed debug prints

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

Changes:
  - all: https://git.openjdk.org/babylon/pull/316/files
  - new: https://git.openjdk.org/babylon/pull/316/files/cc9ab739..8da4431a

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=babylon&pr=316&range=04
 - incr: https://webrevs.openjdk.org/?repo=babylon&pr=316&range=03-04

  Stats: 35 lines in 5 files changed: 14 ins; 2 del; 19 mod
  Patch: https://git.openjdk.org/babylon/pull/316.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/316/head:pull/316

PR: https://git.openjdk.org/babylon/pull/316