RFR: 8355746: Start of release updates for JDK 26

[Nizar Benalla]

Get JDK 26 underway.

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Commit messages:
 - Update copyright years
 - Update --release 25 symbol information for JDK 24 build 20
 - initial commit start-of-JDK-26

Changes: https://git.openjdk.org/jdk/pull/25008/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25008&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8355746
  Stats: 1193 lines in 54 files changed: 1100 ins; 16 del; 77 mod
  Patch: https://git.openjdk.org/jdk/pull/25008.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25008/head:pull/25008

PR: https://git.openjdk.org/jdk/pull/25008