ci: align Java test runtime with latest pre-release tooling

[wenytang-ms]

Problem

CI was failing in the VS Code extension test step after installing the latest redhat.java --pre-release.

The failing tests all called JDT LS delegate commands from the Java test plugin and failed with errors such as:

No delegateCommandHandler for vscode.java.test.junit.argument
No delegateCommandHandler for vscode.java.test.navigateToTestOrTarget
No delegateCommandHandler for vscode.java.test.findTestLocation

This means the Java test plugin bundle was not resolved/loaded into the JDT LS runtime used by the latest Red Hat Java pre-release.

Root cause

CI intentionally installs rolling Java pre-release tooling:

redhat.java --pre-release
vscjava.vscode-java-debug --pre-release

The latest redhat.java pre-release moved to a newer JDT LS / dependency stack. The target platform and packaged server jars therefore need to remain compatible with that rolling stack.

The new stack exposes a few dependency-resolution issues:

• JUnit 5 and JUnit 6 bundles with the same symbolic names now coexist in the target platform.
• In OSGi, bundle-version="5.14.0" is a lower bound, not an exact version, so JUnit 5 requirements can accidentally match JUnit 6 bundles.
• The latest JDT LS stack includes ASM 9.10.1, while JaCoCo 0.8.14 requires ASM < 9.10.
• Some JUnit 5 runtime bundles need to be made explicit so the generated server/ content stays version-consistent.

Fix

Keep CI tracking latest Java pre-release tooling, and make the target platform/runtime explicit enough to resolve consistently:

• Keep the JDT LS target platform on https://download.eclipse.org/jdtls/snapshots/repository/latest/.
• Add explicit OSGi version ranges so JUnit 5 requirements stay on the 5.x / 1.x line and JUnit 6 requirements stay on the 6.x line.
• Add explicit JUnit 5 runtime support bundles (junit-jupiter-migrationsupport, Vintage, Platform runner/suite bundles) at the current 5.14.4 / 1.14.4 line.
• Update JaCoCo core/agent to 0.8.15, which supports ASM 9.10.1.
• Regenerate contributes.javaExtensions from the built server/ artifacts.

The test runner still installs redhat.java --pre-release and vscjava.vscode-java-debug --pre-release, so CI continues to catch future breakages from upstream pre-release changes.

Verification

Local verification:

npm run build-plugin
npm test   # fresh .vscode-test/extensions; installs redhat.java v1.56.2026070709

PR CI is green on Linux, Windows, and macOS.