DifferentialDrivetrainSimTest doesn't converge (sometimes) because of LTVUnicycleController

[Gold856]

DifferentialDrivetrainSimTest.Convergence fails in CI sometimes (1, 2, 3, 4). Earliest failure is from ~2 weeks ago, which correlates with the swap to LTVUnicycleController.

[calcmogul]

Could be measurement noise in the sim. We could try turning that off.

[calcmogul]

We could also address this by hardcoding the random seed for all tests with "Convergence" in their name.