Convert to parcel for frontend builds

[jpellizzari]

Currently EE uses the create-react-app scripts to call webpack for building the frontend bundle. We should convert to parcel for consistency between EE and Core.

This will solve some issues around importing images that are different between the projects, as well as allow us to change out our test runner in the future.

AC:

• "Eject" create react app scripts from EE
• Use parcel for building the FE bundle
• Ensure that all docker image builds still work with the new bundle
• Add jest for running tests
• Clean up CRA dependencies

[lasomethingsomething]

Makes progress on weaveworks/weave-gitops#2321 per @jpellizzari (I removed the link to this private issue that was posted on the public repo and am connecting the issues here for our internal reference). Thanks Jordan for the updates. :)