[code-reflection] Integrated: Experiments with HatPtrOp

[Gary Frost]

Experiments with HatPtrOp to simplify accessing iface mappings when lowering code. 

Also a schema parse fix for simple types.

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Commit messages:
 - Experiments with HatPtrOp

Changes: https://git.openjdk.org/babylon/pull/124/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=124&range=00
  Stats: 45 lines in 4 files changed: 28 ins; 0 del; 17 mod
  Patch: https://git.openjdk.org/babylon/pull/124.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/124/head:pull/124

PR: https://git.openjdk.org/babylon/pull/124