ci: Improve CI performance (no-changelog) (#7637)

1. Split backend and frontend tests to avoid them running in parallel
2. Enable coverage only on `master`

packages/design-system/vite.config.ts

@@ -1,9 +1,30 @@
 import vue from '@vitejs/plugin-vue';
 import { resolve } from 'path';
 import { defineConfig, mergeConfig } from 'vite';
+import { type UserConfig } from 'vitest';
 import { defineConfig as defineVitestConfig } from 'vitest/config';
 
-const { coverageReporters } = require('../../jest.config.js');
+export const vitestConfig = defineVitestConfig({
+	test: {
+		globals: true,
+		environment: 'jsdom',
+		setupFiles: ['./src/__tests__/setup.ts'],
+		...(process.env.COVERAGE_ENABLED === 'true'
+			? {
+					coverage: {
+						provider: 'v8',
+						reporter: require('../../jest.config.js').coverageReporters,
+						all: true,
+					},
+			  }
+			: {}),
+		css: {
+			modules: {
+				classNameStrategy: 'non-scoped',
+			},
+		},
+	},
+}) as UserConfig;
 
 export default mergeConfig(
 	defineConfig({
@@ -35,21 +56,5 @@ export default mergeConfig(
 			},
 		},
 	}),
-	defineVitestConfig({
-		test: {
-			globals: true,
-			environment: 'jsdom',
-			setupFiles: ['./src/__tests__/setup.ts'],
-			coverage: {
-				provider: 'v8',
-				reporter: coverageReporters,
-				all: true,
-			},
-			css: {
-				modules: {
-					classNameStrategy: 'non-scoped',
-				},
-			},
-		},
-	}),
+	vitestConfig,
 );