RFR: JDK-8301447: [REDO] CodeHeap has virtual methods that are not overridden

[Justin King]

Redo [JDK-8301378](https://bugs.openjdk.org/browse/JDK-8301378), this time also fixing the serviceability code.

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Commit messages:
 - Redo removal of virtual methods in CodeHeap

Changes: https://git.openjdk.org/jdk/pull/12345/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12345&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8301447
  Stats: 10 lines in 2 files changed: 0 ins; 5 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/12345.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12345/head:pull/12345

PR: https://git.openjdk.org/jdk/pull/12345