RFR: 8352489: Relax jspawnhelper version checks to informative

[Aleksey Shipilev]

See the bug for rationale. 

This goal for this improvement is to be easily backportable, so we can catch up with update releases. As such, it does a few borderline-trivial changes, and _does not_ change the jspawnhelper protocol. So the overwrite of `jspawnhelper` with this new version would be "compatible" in a very weak sense of the word.

Additional testing:
 - [x] Linux x86_64 server fastdebug, `java/lang/ProcessBuilder`

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Commit messages:
 - Fix

Changes: https://git.openjdk.org/jdk/pull/24127/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24127&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8352489
  Stats: 13 lines in 2 files changed: 2 ins; 3 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/24127.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24127/head:pull/24127

PR: https://git.openjdk.org/jdk/pull/24127