RFR: 8312491: Update Classfile API snippets and examples [v6]

[Adam Sotona]

> This pull request updates Classfile API snippets and examples and adds missing javadoc.
> 
> Please review.
> 
> Thanks,
> Adam

Adam Sotona has updated the pull request incrementally with two additional commits since the last revision:

 - fixing javadoc
 - fixing javadoc

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/14968/files
  - new: https://git.openjdk.org/jdk/pull/14968/files/30d0507a..a2b4e858

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14968&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14968&range=04-05

  Stats: 1464 lines in 3 files changed: 1385 ins; 0 del; 79 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