[rmodels] Consistent DrawBillboardPro with DrawTexturePro (#4132)

* [rmodels] Re-implement `DrawBillboardPro`

* [rmodels] Add comments to `DrawBillboardPro`

* [rmodels] Make `DrawBillboardPro` consistent with `DrawTexturePro`

* Update raylib_api.* by CI

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

parser/output/raylib_api.json

@@ -10400,7 +10400,7 @@
         },
         {
           "type": "float",
-          "name": "size"
+          "name": "scale"
         },
         {
           "type": "Color",

parser/output/raylib_api.lua

@@ -7230,7 +7230,7 @@ return {
         {type = "Camera", name = "camera"},
         {type = "Texture2D", name = "texture"},
         {type = "Vector3", name = "position"},
-        {type = "float", name = "size"},
+        {type = "float", name = "scale"},
         {type = "Color", name = "tint"}
       }
     },

parser/output/raylib_api.txt

@@ -3968,7 +3968,7 @@ Function 466: DrawBillboard() (5 input parameters)
   Param[1]: camera (type: Camera)
   Param[2]: texture (type: Texture2D)
   Param[3]: position (type: Vector3)
-  Param[4]: size (type: float)
+  Param[4]: scale (type: float)
   Param[5]: tint (type: Color)
 Function 467: DrawBillboardRec() (6 input parameters)
   Name: DrawBillboardRec

parser/output/raylib_api.xml

@@ -2645,7 +2645,7 @@
             <Param type="Camera" name="camera" desc="" />
             <Param type="Texture2D" name="texture" desc="" />
             <Param type="Vector3" name="position" desc="" />
-            <Param type="float" name="size" desc="" />
+            <Param type="float" name="scale" desc="" />
             <Param type="Color" name="tint" desc="" />
         </Function>
         <Function name="DrawBillboardRec" retType="void" paramCount="6" desc="Draw a billboard texture defined by source">