Use @-imports in TS runtime code (#50470)

Co-authored-by: Robert Sese <734194+rsese@users.noreply.github.com>

vitest.config.ts

@@ -5,6 +5,11 @@ export default {
     exclude: ['**/tests/playwright-*.spec.ts'],
     // Default is `!process.env.CI`
     watch: false,
+    // vitest doesn't account for tsconfig.json `paths` settings so we have to
+    // manually set this alias to resolve our TS @-imports
+    alias: {
+      '@/': new URL('./src/', import.meta.url).pathname,
+    },
 
     globalSetup: './src/tests/vitest.setup.ts',
   },