Upcast rotated box transforms

[AntoineSimoulin]

Summary

This pull request addresses an issue where performing certain operations on rotated bounding boxes in float16 format could lead to NaN values due to overflow.

Issue Details

The functions _xyxyxyxy_to_xywhr and _parallelogram_to_bounding_boxes involve squaring operations on bounding box coordinates. When using float16 precision, boxes with absolute coordinate values above 256 can result in overflow, as the square of 257 ($257^2 = 66,049$) exceeds the maximum representable value for float16 ($65,504 = (2−2^{−10}) \times 2^{15}$). This leads to unreliable results and NaN values in subsequent computations.

Solution

To address this issue, this PR ensures that the floating point data is upcast to at least float32 for these operations. This increases the maximum representable value, allowing support for box coordinates up to $\sqrt{2^{31} - 1} \approx 46,341$, which should be sufficient for all common computer vision applications.

Additional Improvements

Simplified code related to rotated bounding box conversion by removing unnecessary integer-to-float conversions.
Rotated Bounding Boxes should not be constructed with integer dtype, so these conversions were redundant.

cc @vfdev-5

[pytorch-bot]

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[NicolasHug]

Thanks a lot for noticing the issue and for the fix @AntoineSimoulin . I left a comment below but I'll approve to unblock

[github-actions]

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