[performance metrics] Use engines.pnpm version when setting up the environment (#46787)

plugins/woocommerce/changelog/fix-metrics-tests-pnpm-version-error

@@ -0,0 +1,4 @@
+Significance: patch
+Type: dev
+
+Perf tests: fix environment setup issue

plugins/woocommerce/tests/metrics/utils.js

@@ -1,3 +1,6 @@
+/**
+ * External dependencies
+ */
 import { existsSync, readFileSync } from 'fs';
 
 export function median( array ) {

tools/compare-perf/config.js

@@ -1,13 +1,17 @@
+const packageJson = require( '../../package.json' );
+let pnpm_package = 'pnpm';
+
+if ( packageJson.engines.pnpm ) {
+	pnpm_package = `pnpm@${ packageJson.engines.pnpm }`;
+}
+
 const config = {
 	gitRepositoryURL: 'https://github.com/woocommerce/woocommerce.git',
-	setupTestRunner:
-		'npm install -g pnpm && pnpm install --filter="@woocommerce/plugin-woocommerce" &> /dev/null && cd plugins/woocommerce && pnpm exec playwright install chromium',
-	setupCommand:
-		'npm install -g pnpm && pnpm install &> /dev/null && pnpm build &> /dev/null',
+	setupTestRunner: `npm install -g ${ pnpm_package } && pnpm install --filter="@woocommerce/plugin-woocommerce" &> /dev/null && cd plugins/woocommerce && pnpm exec playwright install chromium`,
+	setupCommand: `npm install -g ${ pnpm_package } && pnpm install &> /dev/null && pnpm build &> /dev/null`,
 	pluginPath: '/plugins/woocommerce',
 	testsPath: '/plugins/woocommerce/tests/metrics/specs',
-	testCommand:
-		'npm install -g pnpm && cd plugins/woocommerce && pnpm test:metrics',
+	testCommand: `npm install -g ${ pnpm_package } && cd plugins/woocommerce && pnpm test:metrics`,
 };
 
 module.exports = config;