Fix redoPlacement exception thrown when rotating the map

[lucaswoj]

In #2648, VectorTileWorker did not implement the redoPlacement method. When this method gets called, such as when the map rotates, an exception is triggered.

This PR restores the redoPlacement method to VectorTileWorkerSource and, by inheritance, GeoJSONWorkerSource

fixes #2983

Checklist

• briefly describe the changes in this PR
• write unit tests for VectorTileWorkerSource#redoPlacement
• write test-suite regression tests for map rotation ticketed in Add tests for the camera API mapbox-gl-test-suite#133
• do a quick sanity check on the debug page
• get a PR review 👍 / 👎