Code review for extracted discussion xblock


Lift and Shift all code: https://github.com/openedx/xblocks-contrib/pull/134
Add discussion service for permission and provider settings: https://github.com/openedx/xblocks-contrib/pull/147
Bundling all JS files with webpack: https://github.com/openedx/xblocks-contrib/pull/155
Allow tests for Extracted & Builtin Discussion XBlock PR: https://github.com/openedx/openedx-platform/pull/37875