Non Square image rasterization for pointclouds

Summary:
Similar to non square image rasterization for meshes, apply the same updates to the pointcloud rasterizer.

Main API Change:
- PointRasterizationSettings now accepts a tuple/list of (H, W) for the image size.

Reviewed By: jcjohnson

Differential Revision: D25465206

fbshipit-source-id: 7370d83c431af1b972158cecae19d82364623380

tests/test_rasterize_points.py

@@ -404,7 +404,7 @@ class TestRasterizePoints(TestCaseMixin, unittest.TestCase):
         torch.manual_seed(231)
         N = 3
         max_P = 1000
-        image_size = 64
+        image_size = (64, 64)
         radius = 0.1
         bin_size = 16
         max_points_per_bin = 500
@@ -501,7 +501,7 @@ class TestRasterizePoints(TestCaseMixin, unittest.TestCase):
             device=device
         )
         # fmt: on
-        image_size = 16
+        image_size = (16, 16)
         radius = 0.2
         bin_size = 8
         max_points_per_bin = 5