[code-reflection] RFR: Sync code gen

[Paul Sandoz]

Ensure code generation is in sync with generated code.

Also, update the `JsonNumber.toNumber` implementation, testing out an alternative approach (slow and functional, performance is not an issue for now).

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Commit messages:
 - Sync code gen.

Changes: https://git.openjdk.org/babylon/pull/369/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=369&range=00
  Stats: 61 lines in 3 files changed: 35 ins; 14 del; 12 mod
  Patch: https://git.openjdk.org/babylon/pull/369.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/369/head:pull/369

PR: https://git.openjdk.org/babylon/pull/369