Add Java 8 support to CI

[c71n93]

Related to #3207

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PR-Codex overview

This PR updates the Java version requirements in pom.xml and the matrix configuration in .github/workflows/mvn.yml to include Java 8.

Detailed summary

• Updated pom.xml to require Java version [8,)
• Updated matrix configuration in .github/workflows/mvn.yml to include Java 8 in the list of supported versions

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