RFR: 1216: Update to JDK 17 and Gradle 7.2

[Erik Joelsson]

This patch bumps the required JDK version to build and run Skara to JDK 17 and the version of Gradle to 7.2. I'm also eliminating some redundant declarations of where to download the JDK binaries so that it's all defined in deps.env.

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Commit messages:
 - SKARA-1216

Changes: https://git.openjdk.java.net/skara/pull/1235/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=1235&range=00
  Issue: https://bugs.openjdk.java.net/browse/SKARA-1216
  Stats: 34 lines in 5 files changed: 10 ins; 0 del; 24 mod
  Patch: https://git.openjdk.java.net/skara/pull/1235.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1235/head:pull/1235

PR: https://git.openjdk.java.net/skara/pull/1235