Fix terrain tile picking in Cesium Inspector

[lilleyse]

Replaced camera.pickEllipsoid with globe.pick so it actually picks terrain instead of the ellipsoid.

Sandcastle - click the top of the mountain in the center

Before

After

[cesium-concierge]

Thanks for the pull request @lilleyse!

• ✔️ Signed CLA found.
• ❔ Unit tests were not updated.
  • Make sure you've updated tests to reflect your changes, added tests for any new code, and ran the code coverage tool.

Reviewers, don't forget to make sure that:

• Cesium Viewer works.
• Works in 2D/CV.
• Works (or fails gracefully) in IE11.

[hpinkos]

Works great @lilleyse, thanks! I'll merge as soon as CI passes

[lilleyse]

@hpinkos I merged in master, this should be ready to go now.