Set Maven compiler release to 17 and restore java17 build

[jtnord]

This library (and more generally all libraries) should not float java versions by picking up the latest from the parent pom.

This library is consumed by plugins, managed outside of Jenkins core (via the plugin-pom) and upgrading the bytecode will cause the plugin pom to no longer work with older (pre 25) versions of Jenkins and there is no need to do that.

Testing done

with java17 prior to this change

[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  2.330 s
[INFO] Finished at: 2026-01-16T10:20:13Z
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-enforcer-plugin:3.6.2:enforce (display-info) on project test-annotations:
[ERROR] Rule 2: org.apache.maven.enforcer.rules.version.RequireJavaVersion failed with message:
[ERROR] Detected JDK C:\Java\jdk-17.0.14+7 is version 17.0.14 which is not in the allowed range [21,).
[ERROR] -> [Help 1]

post this change

[INFO] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.052 s -- in org.jvnet.hudson.test.DummyTest
[INFO]
[INFO] Results:
[INFO]
[INFO] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0
[INFO]
[INFO]
[INFO] --- jar:3.5.0:jar (default-jar) @ test-annotations ---
[INFO] Building jar: D:\source\github\jenkinsci\lib-test-annotations\target\test-annotations-999999-SNAPSHOT.jar
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  4.987 s
[INFO] Finished at: 2026-01-16T10:21:08Z
[INFO] ------------------------------------------------------------------------

jenkinsci/jenkins#26018

Submitter checklist

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• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub or Jira
• Link to relevant pull requests, esp. upstream and downstream changes
• Ensure you have provided tests that demonstrate the feature works or the issue is fixed