[code-reflection] Integrated: added some experiments for testing JavaCodeBuilder and Txfmr

[Gary Frost]

Some experiments for testing txfmr. 

Also moved JavaHATCodeBuilder from tools.  It needs reparenting but is useful for debugging

Found a bug in Txfmr which was stopping us from chaining transformations that removed ops.

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Commit messages:
 - added some experiments for testing JavaCodeBuilder and Txfmr

Changes: https://git.openjdk.org/babylon/pull/795/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=795&range=00
  Stats: 588 lines in 10 files changed: 404 ins; 124 del; 60 mod
  Patch: https://git.openjdk.org/babylon/pull/795.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/795/head:pull/795

PR: https://git.openjdk.org/babylon/pull/795