RFR: 8295857: Clarify that cleanup code can be skipped when the JVM terminates (e.g. when calling halt())

[Brent Christian]

[JDK-8290036](https://bugs.openjdk.org/browse/JDK-8290036) documented the shutdown sequence, noting that calling Runtime.halt() skips the shutdown sequence and immediately terminates the VM. Thus, "threads' current methods do not complete normally or abruptly; no finally clause of any method is executed".

One ramification of this is that resources within try-with-resource blocks will not be released. It would be good to state this explicitly.

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Commit messages:
 - Merge branch 'master' into 8295857
 - update halt() @apiNote
 - update doc changes
 - Update doc for Runtime class and halt() method

Changes: https://git.openjdk.org/jdk/pull/11218/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11218&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8295857
  Stats: 7 lines in 1 file changed: 2 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/11218.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11218/head:pull/11218

PR: https://git.openjdk.org/jdk/pull/11218