7c6f519879
Deletes mj_factorI_legacy and mj_solveLD_legacy from the engine and headers. Updates factorI, solveLD, and inertia benchmarks to remove legacy targets and only benchmark CSR. Rewrites engine_core_smooth_test to verify CSR solver against mj_mulM instead of legacy solver. PiperOrigin-RevId: 942507341 Change-Id: I4281decb7018cfa3e46cb446efd5fe1179f6ae1f