RFR: 8290036: Define and specify Runtime shutdown sequence [v9]

[David Holmes]

On Fri, 30 Sep 2022 21:46:34 GMT, Stuart Marks <smarks at openjdk.org> wrote:

>> The concept of the shutdown sequence needs to be specified more clearly. This PR adds text for this into the class specification of `java.lang.Runtime`. Also includes adjustments to related areas in `addShutdownHook`, `halt`, and in the `System` and `Thread` classes. The changes here should coordinate with similar changes to JLS 12.8, JVMS 5.7, and the Invocation API chapter of the _JNI Specification._
>
> Stuart Marks has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Additional edits to Runtime and Thread specs.

Looks good! Noting further from me. Thanks @stuart-marks !

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Marked as reviewed by dholmes (Reviewer).

PR: https://git.openjdk.org/jdk/pull/9437