Gradle Build: Exact JDK version (major.minor.patch) provisioning

[jjohannes]

The JDK we currently use on CI is 21.0.1. The exact version is important as it is written into module-info.class files. That's why we add it as input. Gradle's toolchain mechanism currently only tracks the major version. That's why we need the full version as a separate input:

https://github.com/hashgraph/hedera-services/blob/develop/build-logic/project-plugins/src/main/kotlin/com.hedera.hashgraph.java.gradle.kts#L126-L130

(Note: the code is not 100% correct atm. It uses the version of the JDK running Gradle. On local machines, this may be a different version than the one provisioned by toolchains if Gradle is started with a different "major" JDK.)

Right now, users starting Gradle with a different JDK than 21.0.1 will not get any remote cache hits for compilation!

If we can't get this working reliably with toolchains (see gradle/gradle#16628 (comment)) we should probably make sure the version we want is exactly the one Gradle was started with and let Gradle use that one. For that we could do a more precise version of the check proposed in: #12780

[jjohannes]

This PR solves this by not using the Gradle Java Toolchains feature anymore: #13108

With future Gradle and Gradle plugin versions, we may be able to move to a better setup. The following things need to be addressed upstream:

• Improvement in Gradle itself - extend JavaToolchainSpec: Allow to specify minor, hotfix and build number for java toolchain gradle/gradle#16628 (comment)
• Improvement in dependency-analysis-plugin: Make FindDeclaredProcsTask use the JDK of the configured Java toolchain to load classes autonomousapps/dependency-analysis-gradle-plugin#1167

[jjohannes]

The implemented solution solves the problem. Closing this issue, since there is nothing we can improve until Gradle core delivers new/better features in the future.