feature: upgrade build from Java 9 to Java 17 (LTS)

[devin-ai-integration]

Summary

Upgrades this educational Maven project's toolchain from Java 9 to Java 17 (LTS). The build was previously pinned to 1.9 and used plugin/dependency versions that predate JDK 17 support. mvn clean verify now passes on JDK 17 with no source-code changes required — all the Streams/Lambda/CompletableFuture examples compile unmodified.

pom.xml changes

• Compiler target 1.9 → 17: replaced the maven-compiler-plugin <source>1.9</source>/<target>1.9</target> with a single <release>17</release> (also surfaced as the maven.compiler.release property).
• maven-compiler-plugin 3.1 → 3.11.0: 3.1 cannot emit class file version 61 / doesn't understand <release>.
• maven-shade-plugin: pinned to 3.4.1 (was unversioned, which resolved to an ancient default that fails on JDK 17's ASM/bytecode level). The benchmark uber-jar (benchmarks.jar) still builds.
• JMH 1.17.4 → 1.37 (via a jmh.version property): older JMH bundles an ASM that rejects Java 17 bytecode during annotation processing.
• JUnit 4.11 → 4.13.2: small bump for a JDK 17–clean test dependency.
• Added dependency-reduced-pom.xml (generated by the shade plugin) to .gitignore.

Code changes

None. No examples used APIs removed/changed after Java 9, so no migration edits were needed.

Validation

mvn clean verify on java -version = 17.0.19 → BUILD SUCCESS. The repo has no src/test test classes, so there were no existing tests to run; surefire reported no tests and the build (incl. shade packaging) completes cleanly.

Residual risks

• No automated tests exist in the repo, so validation is limited to successful compilation + packaging.
• The shade plugin logs benign "overlapping resources" (LICENSE / MANIFEST.MF) warnings from the JMH/JUnit jars — cosmetic, not failures.
• There is no CI workflow (adding one was optional per the task and not included).

Link to Devin session: https://app.devin.ai/sessions/267a079877f94aa19879f0ceb6c2f2c8
Requested by: @vibhaseshadri-cognition

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