feat: Add plugin slot for login page

This change adds a plugin slot for the login page allowing it to be customised.

Since there was a dependency conflict between frontend-plugin-framework and the react-hooks testing package, the react-hooks testing package has been removed and a replaced with a simple mechanism for testing hooks.

Since this touched the Login Page those have also been refactored to move away from redux connect.

package.json

@@ -39,11 +39,11 @@
     "@fortawesome/free-brands-svg-icons": "6.7.2",
     "@fortawesome/free-solid-svg-icons": "6.7.2",
     "@fortawesome/react-fontawesome": "0.2.2",
+    "@openedx/frontend-plugin-framework": "^1.4.0",
     "@openedx/paragon": "^22.1.1",
     "@optimizely/react-sdk": "^2.9.1",
     "@redux-devtools/extension": "3.3.0",
     "@testing-library/react": "^12.1.5",
-    "@testing-library/react-hooks": "^8.0.1",
     "algoliasearch": "^4.14.3",
     "algoliasearch-helper": "^3.14.0",
     "classnames": "2.5.1",