[code-reflection] RFR: ExplicitOnnxOps.If implementation of captured values and initializers [v2]

[Adam Sotona]

> Deconstruction of `OnnxTransformer` into multiple steps with support for captured values and initializers in nested bodies of `If` op.

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

  improved test

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

Changes:
  - all: https://git.openjdk.org/babylon/pull/353/files
  - new: https://git.openjdk.org/babylon/pull/353/files/8aa07ecc..c135238e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=babylon&pr=353&range=01
 - incr: https://webrevs.openjdk.org/?repo=babylon&pr=353&range=00-01

  Stats: 21 lines in 1 file changed: 14 ins; 2 del; 5 mod
  Patch: https://git.openjdk.org/babylon/pull/353.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/353/head:pull/353

PR: https://git.openjdk.org/babylon/pull/353