RFR: JDK-8296149: Start of release updates for JDK 21 [v4]

[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 pull request now contains 19 commits:

 - Merge branch 'master' into JDK-8296149
 - Merge branch 'master' into JDK-8296149
 - Merge branch 'master' into JDK-8296149
 - 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
 - ... and 9 more: https://git.openjdk.org/jdk/compare/0d2a9ee5...e252e83a

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Changes: https://git.openjdk.org/jdk/pull/10924/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10924&range=03
  Stats: 3717 lines in 70 files changed: 3672 ins; 1 del; 44 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