[code-reflection] Integrated: Migrated BufferTagger to use InvokeOpHelper for common tasks

[Gary Frost]

Refactored  BufferTagger to use InvokeOpHelper 

It's useful for common HAT style patterns,

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Commit messages:
 - Migrated BufferTagger to use InvokeOpHelper for common tasks

Changes: https://git.openjdk.org/babylon/pull/800/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=800&range=00
  Stats: 129 lines in 2 files changed: 42 ins; 19 del; 68 mod
  Patch: https://git.openjdk.org/babylon/pull/800.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/800/head:pull/800

PR: https://git.openjdk.org/babylon/pull/800