Extend extension integration-tests for node environment

[joao-boechat]

This PR adds Electron (Node.js) test execution to the VS Code integration test suites, which previously only ran in the browser via @vscode/test-web. Tests now run in both environments to catch platform-specific issues.

[Copilot]

Pull request overview

This PR updates the VS Code extension integration test infrastructure to run suites in both VS Code for the Web (Chromium) and VS Code Desktop (Electron), with separate bundling and entrypoints per environment.

Changes:

• Add separate Mocha runners and suite entrypoints for browser vs. Electron extension hosts.
• Update the test runner to execute each suite via @vscode/test-web and (for non-empty suites) @vscode/test-electron.
• Adjust CI pipelines to use xvfb-run where needed and add the Electron test harness dependency.

Reviewed changes

Copilot reviewed 14 out of 18 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
source/vscode/test/suites/runNode.ts	New Mocha runner for Electron extension host.
source/vscode/test/suites/runBrowser.ts	New Mocha runner for VS Code Web extension host.
source/vscode/test/suites/language-service/index.node.ts	New node/Electron entrypoint and local fake GitHub server for language-service suite.
source/vscode/test/suites/language-service/index.browser.ts	Switch to browser runner and configure fake GitHub endpoint for web runs.
source/vscode/test/suites/extensionUtils.ts	Add configurable GitHub endpoint used during test activation.
source/vscode/test/suites/empty/index.browser.ts	Add no-op “empty” suite for environment dry-run.
source/vscode/test/suites/debugger/qsharp.test.ts	Make debugger assertions/config paths compatible across web + node.
source/vscode/test/suites/debugger/openqasm.test.ts	Make debugger assertions/config paths compatible across web + node.
source/vscode/test/suites/debugger/index.node.ts	Switch node suite entrypoint to Electron runner.
source/vscode/test/suites/debugger/index.browser.ts	Add browser suite entrypoint for debugger tests.
source/vscode/test/runTests.mjs	Run suites in both web and Electron environments; update output paths.
source/vscode/test/buildTests.mjs	Build separate browser/node test bundles via esbuild.
package.json	Add @vscode/test-electron dependency.
package-lock.json	Lockfile updates for Electron test harness and transitive deps.
.gitignore	Ignore .vscode-test/ artifacts (Electron test downloads).
.github/workflows/multiplat.yml	Use xvfb-run for Linux integration tests.
.github/workflows/ci.yml	Wrap integration tests with xvfb-run on ubuntu CI job.
.ado/publish.yml	Update display name and run integration tests under xvfb-run.