Animation: Sensible frame range for motion paths

Motion paths can now be initialised to more sensible frame ranges,
rather than simply 1-250:

- Scene Frame Range
- Selected Keyframes
- All Keyframes

The Motion Paths operators are now also added to the Object context menu
and the Dopesheet context menu.

The scene range operator was removed, because the operators now
automatically find the range when baking the motion paths.

The clear operator now appears separated in "Selected Only" and "All",
because it was not clear for the user what the button was doing.

Reviewed By: sybren, looch

Maniphest Tasks: T93047

Differential Revision: https://developer.blender.org/D13687

source/blender/blenkernel/intern/anim_visualization.c

@@ -153,6 +153,11 @@ bMotionPath *animviz_verify_motionpaths(ReportList *reports,
     if ((mpath->start_frame != mpath->end_frame) && (mpath->length > 0)) {
       /* outer check ensures that we have some curve data for this path */
       if (mpath->length == expected_length) {
+        /* The length might be the same, but the start and end could be different */
+        if (mpath->start_frame != avs->path_sf) {
+          mpath->start_frame = avs->path_sf;
+          mpath->end_frame = avs->path_ef;
+        }
         /* return/use this as it is already valid length */
         return mpath;
       }