ci: run Java build and tests on larger runners

[ankitTelnyx]

Summary

• run the production Java SDK build and test jobs on GitHub's 16-core hosted runners
• preserve the existing 30-minute job timeout and required check names
• prevent standard ubuntu-latest runners from shutting down before the generated SDK test suite completes

Evidence

• release PR release: 6.86.0 #216 test run 31797977144 was cancelled twice during :telnyx-proguard-test:proguardJar after the runner received a shutdown signal
• the generated tree itself already passed staging CI on a larger runner
• the production repo has no access to the staging repository's telnyx-4xlarge runner group, so this uses the available GitHub-hosted large-runner label
• actionlint and git diff --check pass

Follow-up

After this PR merges, rerun staging promotion so next and release PR #216 receive the production-owned CI workflow, then validate the release end-to-end.