MM-63669 E2E/Playwright: Move "e2e-tests/playwright/test" to "e2e-tests/playwright" folder (#30647)

* move "e2e-tests/playwright/test" to  "e2e-tests/playwright/test" and expose "ensurePluginsLoaded"

* add test setup, and expose ensurePluginsLoaded and ensureServerDeployment to pw

e2e-tests/playwright/script/post_install.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+
+if [ -n "$PLAYWRIGHT_SKIP_BROWSER_DOWNLOAD" ]; then
+    echo "Skipped browsers download for Playwright"
+    exit 0
+fi
+
+# Install needed Playwright browsers only -- chromium and firefox only for these are the ones being used by the tests.
+# May add more browsers in the future.
+# https://playwright.dev/docs/library#browser-downloads
+npx playwright install chromium
+npx playwright install firefox