VM and core-libs sealed classes update

[hseigel]

Push latest reviewed VM and core-libs changes into sealed-types repo.

---

Progress

• Change must not contain extraneous whitespace

Download

$ git fetch https://git.openjdk.java.net/amber pull/23/head:pull/23
$ git checkout pull/23

[bridgekeeper]

👋 Welcome back hseigel! A progress list of the required criteria for merging this PR into sealed-types will be added to the body of your pull request.

[openjdk]

@hseigel This change now passes all automated pre-integration checks, type /integrate in a new comment to proceed. After integration, the commit message will be:

VM and core-libs sealed classes update

• If you would like to add a summary, use the /summary command.
• To credit additional contributors, use the /contributor command.
• To add additional solved issues, use the /issue command.

There are currently no new commits on the sealed-types branch since the last update of the source branch of this PR. If another commit should be pushed before you perform the /integrate command, your PR will be automatically rebased. If you would like to avoid potential automatic rebasing, specify the current head hash when integrating, like this: /integrate b37f74674c3ae93c925f0f204c9f1c8759c53bd1.

➡️ To integrate this PR with the above commit message to the sealed-types branch, type /integrate in a new comment.

[mlbridge]

Webrevs

• 00: Full (02ad252)

[hseigel]

/integrate

[openjdk]

@hseigel
Pushed as commit a50af77.