RFR: JDK-8296149: Start of release updates for JDK 21 [v3]

[Joe Darcy]

> Usual start-of-release updates. Symbol updates in initial version reflect JDK 20 build 21.

Joe Darcy has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 16 additional commits since the last revision:

 - Merge branch 'master' into JDK-8296149
 - Merge branch 'master' into JDK-8296149
 - Update symbol information for JDK 20 build 26.
 - Merge branch 'master' into JDK-8296149
 - Merge branch 'master' into JDK-8296149
 - Fix failed HotSpot regression tests.
 - Merge branch 'master' into JDK-8296149
 - Update symbol information to JDK 20 build 24.
 - Merge branch 'master' into JDK-8296149
 - Merge branch 'master' into JDK-8296149
 - ... and 6 more: https://git.openjdk.org/jdk/compare/7be0c7e6...515002c7

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/10924/files
  - new: https://git.openjdk.org/jdk/pull/10924/files/89731cb2..515002c7

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10924&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10924&range=01-02

  Stats: 14769 lines in 190 files changed: 1917 ins; 12471 del; 381 mod
  Patch: https://git.openjdk.org/jdk/pull/10924.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10924/head:pull/10924

PR: https://git.openjdk.org/jdk/pull/10924