RFR: 7903928: update build.gradle to use JDK 23

[Nizar Benalla]

We've updated native makefile to use JDK 23 (https://github.com/openjdk/jextract/commit/0b89a462146940a2ec90e34eeb5df3d46d8980d2), build.gradle works & expects jdk 23, it still refers to JDK var as "jdk22_home" and passes --release to be 22. Also jextract version is "22".

The mismatch has caused [some confusion](https://mail.openjdk.org/pipermail/panama-dev/2025-January/020915.html).

This patch to rename references to `jdk22_home` to `jdk_home`, the jextract version has now been bumped to `23`.

This PR has been obtained through a `git merge --squash` of #271.

TIA

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Commit messages:
 - Updates based on review comment in pr/271
 - jextract PR #271

Changes: https://git.openjdk.org/jextract/pull/275/files
  Webrev: https://webrevs.openjdk.org/?repo=jextract&pr=275&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903928
  Stats: 14 lines in 4 files changed: 2 ins; 0 del; 12 mod
  Patch: https://git.openjdk.org/jextract/pull/275.diff
  Fetch: git fetch https://git.openjdk.org/jextract.git pull/275/head:pull/275

PR: https://git.openjdk.org/jextract/pull/275