RFR: 8331873: Improve/expand info in `New API In` on Help page [v2]

[Nizar Benalla]

> This PR supersedes #19222, I've resolved the merge conflicts and updated the text based on review comments.

Nizar Benalla has updated the pull request incrementally with one additional commit since the last revision:

  Update TestNewApiList

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/23269/files
  - new: https://git.openjdk.org/jdk/pull/23269/files/f45df69b..128ada03

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23269&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23269&range=00-01

  Stats: 5 lines in 1 file changed: 0 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/23269.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23269/head:pull/23269

PR: https://git.openjdk.org/jdk/pull/23269