Optimized manim.utils.bezier.get_smooth_cubic_bezier_handle_points() (#3767)

* Optimized manim.utils.get_smooth_cubic_bezier_handle_points()

* Fixed typo in docstring regarding vector u

* Add tests for get_smooth_cubic_bezier_handle_points

* Fix backreference in test docstrings

Co-authored-by: adeshpande <[email protected]>

---------

Co-authored-by: adeshpande <[email protected]>

Author: chopan050

manim/mobject/types/vectorized_mobject.py

@@ -31,7 +31,7 @@
 from manim.utils.bezier import (
     bezier,
     bezier_remap,
-    get_smooth_handle_points,
+    get_smooth_cubic_bezier_handle_points,
     integer_interpolate,
     interpolate,
     partial_bezier_points,
@@ -1093,7 +1093,7 @@ def change_anchor_mode(self, mode: Literal["jagged", "smooth"]) -> Self:
                 # The append is needed as the last element is not reached when slicing with numpy.
                 anchors = np.append(subpath[::nppcc], subpath[-1:], 0)
                 if mode == "smooth":
-                    h1, h2 = get_smooth_handle_points(anchors)
+                    h1, h2 = get_smooth_cubic_bezier_handle_points(anchors)
                 else:  # mode == "jagged"
                     # The following will make the handles aligned with the anchors, thus making the bezier curve a segment
                     a1 = anchors[:-1]