E2E: Add support for building test plugins (#91873)

* build test apps with webpack

* add extensions test app

* update e2e tests

* remove non-build test apps using amd

* use @grafana/plugin-configs rather than create-plugin config

* Update e2e/plugin-e2e/plugin-e2e-api-tests/as-admin-user/extensions/usePluginComponents.spec.ts

Co-authored-by: Jack Westbrook <jack.westbrook@gmail.com>

* Update package.json

Co-authored-by: Jack Westbrook <jack.westbrook@gmail.com>

* use run dir variable instead of hardcoded path

* add dummy licence file

* add separate step for building test plugins

* support nested plugins

* remove react-router-dom from the externals array

* remove add_mode dev

* lint starlark

* pass license path as env variable

* fix the path

* chore(e2e-plugins): clean up dependencies to match core versions

* refactor(e2e-plugins): prefer extending webpack plugins-config

* docs(e2e-plugins): add basic info to extensions test plugin readme

* update readme

* change dir name from custom plugins to test plugins

* change root readme

* update lockfile

---------

Co-authored-by: Jack Westbrook <jack.westbrook@gmail.com>

devenv/plugins.yaml

@@ -1,27 +1,19 @@
 apiVersion: 1
 
 apps:
-  - type: myorg-extensions-app
+  - type: grafana-extensionstest-app
     org_id: 1
     org_name: Main Org.
     disabled: false
-  - type: myorg-a-app
+    jsonData:
+      apiUrl: http://default-url.com
+    secureJsonData:
+      apiKey: secret-key
+  - type: grafana-extensionexample1-app
     org_id: 1
     org_name: Main Org.
     disabled: false
-  - type: myorg-b-app
-    org_id: 1
-    org_name: Main Org.
-    disabled: false
-  - type: myorg-extensionpoint-app
-    org_id: 1
-    org_name: Main Org.
-    disabled: false
-  - type: myorg-componentconsumer-app
-    org_id: 1
-    org_name: Main Org.
-    disabled: false
-  - type: myorg-componentexposer-app
+  - type: grafana-extensionexample2-app
     org_id: 1
     org_name: Main Org.
     disabled: false