RFR: 8312491: Update Classfile API snippets and examples

[Adam Sotona]

8312491: Update Classfile API snippets and examples

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Commit messages:
 - 8312491: Update Classfile API snippets and examples

Changes: https://git.openjdk.org/jdk/pull/14968/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14968&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8312491
  Stats: 73 lines in 3 files changed: 40 ins; 0 del; 33 mod
  Patch: https://git.openjdk.org/jdk/pull/14968.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14968/head:pull/14968

PR: https://git.openjdk.org/jdk/pull/14968