VideoPress: make video dashboard works with private media endpoint

The VideoPress video dashboard uses the core `/media` endpoint to list and search videos, but [it does an unauthenticated request](https://github.com/Automattic/jetpack/blob/trunk/projects/packages/videopress/src/client/state/resolvers.js#L139) to it.

Some users may want to turn the core `/media` endpoint private to prevent their videos from being listed by non-logged-in people. In this case, the VideoPress dashboard will not work properly.

We may need to investigate if it's possible to perform an authenticated request so even these users with private `/media` endpoints could use the VideoPress dashboard.

Start in projects/packages/videopress/src/client/state/resolvers.js around line 139 and trace how the VideoPress dashboard lists and searches videos through the core /media endpoint. Investigate the existing authenticated request path, then verify that the dashboard works for users with a private /media endpoint while unauthenticated users cannot list those videos.

Written by the indexing model from the issue text.