RFR: 8353439: Shell grouping of -XX:OnError= commands is surprising

[Kevin Walls]

We should be consistent, and run all OnError items in a new shell.  Currently the ; separator causes a new shell, but multiple -XX:OnError= options are grouped into the same shell.

next_OnError_command() decides on where a new command starts.  It should recognise newlines, and all commands will get their own shell.

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Commit messages:
 - Recognise newlines in next_OnError_command

Changes: https://git.openjdk.org/jdk/pull/24354/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24354&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8353439
  Stats: 3 lines in 1 file changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/24354.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24354/head:pull/24354

PR: https://git.openjdk.org/jdk/pull/24354