[code-reflection] Integrated: Rationalised HatPtr and Types. Moved from experiments to hat

[Gary Frost]

Moved HatPtr and Type from experiments to hat package. 

Added DebugBackend. To simplify debugging...

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Commit messages:
 - Rationalised HatPtr and Types.  Moved from experiments to hat

Changes: https://git.openjdk.org/babylon/pull/168/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=168&range=00
  Stats: 2017 lines in 13 files changed: 843 ins; 1147 del; 27 mod
  Patch: https://git.openjdk.org/babylon/pull/168.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/168/head:pull/168

PR: https://git.openjdk.org/babylon/pull/168