[Feature] Support PrRoIPool operation (#2113)

* support prroipooling

* fix build bug

* fix bug of precision

* fix lint

* add ut

* add license and citation

* polish op and add type hint

* refactor ut

* add docstring for prroipool

* polish code

* format cu and cuh code

* fix format

* fix format

* fix typo

Co-authored-by: zhouzaida <zhouzaida@163.com>
Co-authored-by: Zaida Zhou <58739961+zhouzaida@users.noreply.github.com>

docs/en/understand_mmcv/ops.md

@@ -57,3 +57,4 @@ We implement common ops used in detection, segmentation, etc.
 | TINShift                     |     | √    | √   |     |
 | UpFirDn2d                    |     | √    |     |     |
 | Voxelization                 | √   | √    |     |     |
+| PrRoIPool                    |     | √    |     |     |

docs/zh_cn/understand_mmcv/ops.md

@@ -57,3 +57,4 @@ MMCV 提供了检测、分割等任务中常用的算子
 | TINShift                     |     | √    | √   |     |
 | UpFirDn2d                    |     | √    |     |     |
 | Voxelization                 | √   | √    |     |     |
+| PrRoIPool                    |     | √    |     |     |

mmcv/ops/__init__.py

@@ -46,6 +46,7 @@
                               points_in_boxes_part)
 from .points_in_polygons import points_in_polygons
 from .points_sampler import PointsSampler
+from .prroi_pool import PrRoIPool, prroi_pool
 from .psa_mask import PSAMask
 from .riroi_align_rotated import RiRoIAlignRotated, riroi_align_rotated
 from .roi_align import RoIAlign, roi_align
@@ -100,5 +101,6 @@
     'SparseConvTensor', 'scatter_nd', 'points_in_boxes_part',
     'points_in_boxes_cpu', 'points_in_boxes_all', 'points_in_polygons',
     'min_area_polygons', 'active_rotated_filter', 'convex_iou', 'convex_giou',
-    'diff_iou_rotated_2d', 'diff_iou_rotated_3d', 'chamfer_distance'
+    'diff_iou_rotated_2d', 'diff_iou_rotated_3d', 'chamfer_distance',
+    'PrRoIPool', 'prroi_pool'
 ]