[code-reflection] RFR: Remove noModuleOp and bufferTagging flags

[Ruby Chen]

Phase out the backend that doesn't use `ModuleOp`. Also make `bufferTagging` run by default.

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Commit messages:
 - Remove noModuleOp and bufferTagging flags

Changes: https://git.openjdk.org/babylon/pull/599/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=599&range=00
  Stats: 112 lines in 12 files changed: 15 ins; 77 del; 20 mod
  Patch: https://git.openjdk.org/babylon/pull/599.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/599/head:pull/599

PR: https://git.openjdk.org/babylon/pull/599