feat: support additional Java test source paths

[Vinay Kumar Maheshwaram (sudovinay01)]

Why this is needed

The Java Test Runner currently discovers test files from source roots classified as test roots by the Java project model. In Gradle projects, src/main/java remains a main source root, so TestNG classes there can compile but are not discovered for editor test actions or Test Explorer. Reclassifying that directory as a Gradle test source set would change build semantics and is not appropriate for projects that intentionally keep these classes in main sources.

IntelliJ IDEA and Eclipse already discover tests in both main and test source folders and provide run/debug actions for them. This change brings that IDE-level discovery capability to VS Code as an opt-in, without changing Gradle source-set classification or task behavior.

What this changes

• Adds the opt-in, workspace-scoped java.test.additionalTestSourcePaths setting. Its default is an empty array, preserving existing behavior.
• Accepts literal source paths or workspace-relative glob patterns and expands glob matches into source directories. The glob library is declared as a production dependency.
• Includes resolved roots in source-path checks and file watching, scans existing Java files with bounded concurrency, and applies Test Explorer updates sequentially.
• Clears cached paths and rebuilds discovery when this setting changes or the user refreshes the Testing view. Overlapping refresh requests are serialized to avoid watcher races.
• Uses stable workspace URI keys, ignores nonexistent literal directories, reports glob errors in the Test Runner for Java Output channel, and deduplicates roots.
• Logs a heads-up when patterns match more than 100 directories; no hard limit is imposed.
• Does not modify Gradle source-set configuration or task behavior.

Configuration example

{
  "java.test.additionalTestSourcePaths": ["app/**/src/main/java"]
}

Reproducer

The manual acceptance project is available at https://github.com/sudovinay01/repro-java-issue.

Validation

• npm test: 165 extension tests passed; activation test passed.
• npm run lint passed.
• Production webpack bundle compiled successfully.
• Regression tests verify additional roots are watched and overlapping refresh requests are serialized.
• Manual reproducer check: AppMainSourceTest and AppTest appeared in Test Explorer and both passed (2/2).

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[Vinay Kumar Maheshwaram (sudovinay01)]

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[Vinay Kumar Maheshwaram (sudovinay01)]

Could a maintainer please help triage this PR or assign a reviewer when available? It has been open since September 26, and I would appreciate guidance on whether any changes are needed before review. Thank you.

[Vinay Kumar Maheshwaram (sudovinay01)]

Merged current upstream main into this branch in fcb779f and regenerated package-lock.json from the merged manifest, preserving glob as a production dependency. Validation passed: npm ci, npm run compile, npm run lint, npm run vscode:prepublish, npm run build-plugin, and npm test (165 extension tests plus the unmanaged-folder test). GitHub now reports the PR as mergeable.