Make Blob info available through GraphQL

As we are working on refactoring the repository view we need also the blob information that is currently delivered through the REST API call as a GraphQL Model. Except the rendered Blob View which will be now replaced by client side rendering.

Of the fields you asked for in #323195 (comment 531167716) , some already existed, some turn out to be the same content as already-existing fields.

A checklist of requested fields:

• Already exists on master
  • name
  • path (needed for copy to clipboard)
• Implementation completed in !58906 (merged)
  • editBlobPath
  • rawPath
  • replacePath (endpoint used for replace button)
  • storedExternally
  • fileType (e.g. 'text')
  • size
  • rawSize
  • simpleViewer (similar to snippets graphql endpoint, to determine which viewer to use on the FE)
  • richViewer (similar to snippets graphql endpoint, to determine which viewer to use on the
  • rawBlob (unmodified text?)
  • plainData !61016 (merged)
  • ideEditPath !61155 (merged)
  • canModifyBlob !61155 (merged)
  • externalStorageUrl !61155 (merged)
  • forkAndEditPath, ideForkAndEditPath !61155 (merged)
  • project { pathLocks !61380 (merged)
• Don't need to implement
  • deletePath (duplicate of webPath)
  • type (e.g. 'simple')
  • tooLarge (too large to view)
  • canLock (in pathLocks)
  • isLocked (in pathLocks)
  • lockLink (make pathLocks mutation instead)

!58677 (merged) added a RepositoryBlob + new GraphQL endpoint to access it.