upgraded to Java 17

[qcdyx]

Summary:

• Update project pom.xml and resolve dependency errors
• Audit plugin/dependency compatibility in gtfs-realtime-validator-webapp/pom.xml and gtfs-realtime-validator-lib/pom.xml (maven-compiler-plugin, maven-surefire-plugin, maven-shade-plugin).

Expected behavior:

Explain and/or show screenshots for how you expect the pull request to work in your testing (in case other devices exhibit different behavior).

Please make sure these boxes are checked before submitting your pull request - thanks!

• Run the unit tests with mvn test to make sure you didn't break anything
• Format the title like "feat: {new feature short description}" or "fix: {describe what was fixed}". Title must follow the Conventional Commit Specification (https://www.conventionalcommits.org/en/v1.0.0/).
• Linked all relevant issues
• Include screenshot(s) showing how this pull request works and fixes the issue(s)

[qcdyx]

Blocked by #199

[qcdyx]

Pushed a fix that increased the database connection pool from 1 to 10, closed a leaked session in getSessionData(), made closeSession() roll back active transactions before closing, added try-finally blocks around all session usage to prevent leaks on exceptions, and changed two HQL queries in BackgroundTask to use Java property paths (gtfsRtFeedModel.gtfsRtId, gtfsFeedModel.feedId) instead of database column names (rtFeedId, gtfsFeedID) which Hibernate 6 no longer accepts.

Tested locally, works well.

[davidgamez]

LGTM