Switch mjData.{qH,qLD} from reduced ("C") to full ("M") inertia matrix structure. No performance impact of extra zeros because of existing "simple dof" skipping mechanism.

PiperOrigin-RevId: 733523931
Change-Id: Ic8d8a152dda5532331c239cb6b4ce7d8d09b7fff

test/engine/engine_support_test.cc

@@ -32,7 +32,6 @@ namespace {
 using ::std::vector;
 using ::testing::ContainsRegex;  // NOLINT
 using ::testing::DoubleNear;
-using ::testing::ElementsAreArray;
 using ::testing::Eq;
 using ::testing::MatchesRegex;
 using ::testing::NotNull;