Update junit5 to 5.14.2

This MR is required for updating Apache BCEL to resolve Java 25 FTBFS 1108557. Java 25 support was added in 5.11.4[1], 5.14.2 is the latest upstream release of JUnit 5. This MR depends on opentest4j-reporting!1

Changes:

• vendor JRE.java (produced by Java Template Engine[2]) that is not packaged yet, add d/README.source with notes on how to produce the file.
• Depend on updated opentest4j-reporting
• debian/patches/16-maven-build.patch - add new opentest4j-reporting artifacts
• debian/patches/17-backward-compatibility.patch - refresh patch.
• Bump standards-version to 4.7.3, remove priority field.

Testing:

• rebuild of reverse-dependencies[3]
• build in sid chroot (updated opentest4j-reporting installed)
• build in sid chroot with default Java 25(updated opentest4j-reporting installed)

[1] https://docs.junit.org/5.11.4/release-notes/

[2] https://jte.gg/

[3] https://launchpad.net/~vpa1977/+archive/ubuntu/bcel-rdeps