[code-reflection] Integrated: Added HatVarOp marker interface and OpTk helpers

[Gary Frost]

Added HATVarOp marker interface to group HATOp's yielding a varName;

Also added some OpTk helpers to simplyfy selecting op's for transformations.

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Commit messages:
 - Added HatVarOp marker interface and OpTk helpers

Changes: https://git.openjdk.org/babylon/pull/755/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=755&range=00
  Stats: 95 lines in 6 files changed: 37 ins; 13 del; 45 mod
  Patch: https://git.openjdk.org/babylon/pull/755.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/755/head:pull/755

PR: https://git.openjdk.org/babylon/pull/755