[code-reflection] Integrated: Refactor/Simplify CallGraph using OpHelpers

[Gary Frost]

First pass at simplifying CallGraph using OpHelpers

I think we need to separate filtering calls from collecing buffer accesses. I will tackle that next .

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Commit messages:
 - Refactor/Simplify  CallGraph using OpHelpers

Changes: https://git.openjdk.org/babylon/pull/884/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=884&range=00
  Stats: 80 lines in 4 files changed: 15 ins; 27 del; 38 mod
  Patch: https://git.openjdk.org/babylon/pull/884.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/884/head:pull/884

PR: https://git.openjdk.org/babylon/pull/884