Add mju_clip, mju_fill, mju_eye and mju_symmetrize to python bindings.

- Also change signatures of `mju_fill` and `mju_symmetrize` to conform to standard.

PiperOrigin-RevId: 485613824
Change-Id: I8dd618bac92ef40aa6c76380fa73302e81968687

python/mujoco/bindings_test.py

@@ -1049,6 +1049,27 @@ Euler integrator, semi-implicit in velocity.
     rank = mujoco.mju_boxQP(res, r, index, h, g, lower, upper)
     self.assertGreater(rank, -1)
 
+  def test_mju_fill(self):
+    res = np.empty(3, np.float64)
+    mujoco.mju_fill(res, 1.5)
+    np.testing.assert_array_equal(res, np.full(3, 1.5))
+
+  def test_mju_eye(self):
+    eye4 = np.empty((4, 4), np.float64)
+    mujoco.mju_eye(eye4)
+    np.testing.assert_array_equal(eye4, np.eye(4))
+
+  def test_mju_symmetrize(self):
+    mat = np.linspace(0, 1, 16).reshape(4, 4)
+    res = np.empty((4, 4), np.float64)
+    mujoco.mju_symmetrize(res, mat)
+    np.testing.assert_array_equal(res, 0.5*(mat + mat.T))
+
+  def test_mju_clip(self):
+    self.assertEqual(mujoco.mju_clip(1.5, 1.0, 2.0), 1.5)
+    self.assertEqual(mujoco.mju_clip(1.5, 2.0, 3.0), 2.0)
+    self.assertEqual(mujoco.mju_clip(1.5, 0.0, 1.0), 1.0)
+
   def test_mju_mul_vec_mat_vec(self):
     vec1 = np.array([1., 2., 3.])
     vec2 = np.array([3., 2., 1.])