RFR: 8325621: Improve jspawnhelper version checks [v2]

[Chad Rakoczy]

> Fix for [8325621](https://bugs.openjdk.org/browse/JDK-8325621)
> 
> Updates jspawnhelper to check that JDK version and jspawnhelper version are the same. Updates test to include check for version. Also tested manually by replacing jspawnhelper with incorrect version to confirm that check works.

Chad Rakoczy has updated the pull request incrementally with one additional commit since the last revision:

  Code cleanup

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/18204/files
  - new: https://git.openjdk.org/jdk/pull/18204/files/cf3c20fb..7bbcc08f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18204&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18204&range=00-01

  Stats: 48 lines in 4 files changed: 16 ins; 24 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/18204.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18204/head:pull/18204

PR: https://git.openjdk.org/jdk/pull/18204