fix: avoid waiting for inherited Edge stdio

[mturac]

Fixes #41210

Summary

• add an internal process launcher option for browser processes whose helpers can inherit stdio and outlive the main process
• use that path for msedge* channels so browser.close() can finish after the browser process exits
• add regression coverage with a Node child that leaves an inherited-stdio grandchild running

Testing

• npm run build
• npm run ttest -- process-launcher.spec.ts
• npm run tsc -- --pretty false
• npx eslint packages/utils/processLauncher.ts packages/playwright-core/src/server/browserType.ts tests/playwright-test/process-launcher.spec.ts
• git diff --check