RFR: 8347063: Add comments in ClassFileFormatVersion for class file format evolution history

[Chen Liang]

`javax.lang.model.SourceVersion` has a series of comments describing the new language features present in each source version. Similar comments for the `ClassFileFormatVersion` would be helpful, so readers no longer need to search through the JVMS to find changes in new versions.

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Commit messages:
 - CFFV evolution comments

Changes: https://git.openjdk.org/jdk/pull/22934/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22934&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8347063
  Stats: 36 lines in 1 file changed: 35 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/22934.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22934/head:pull/22934

PR: https://git.openjdk.org/jdk/pull/22934