graphics: BitMapScale() broken for upscales, disagrees with OS3.x when downscaling

I just added some BitMapScale() tests in P96CTS.

## AmigaOS P96 8bpp

This are the golden files drawn by the P96 softrast at depth 8

BitMapScale-down:
<img width="320" height="200" alt="Image" src="https://github.com/user-attachments/assets/b707c301-b2e7-48d1-9979-251bbf33b00e" />

BitMapScale-up:
<img width="320" height="200" alt="Image" src="https://github.com/user-attachments/assets/2cc977cb-5944-4b99-b902-09501cea96f4" />


## AROS amigavideo & Z3660

An AROS, downscaling seems to disagree on sampling / rounding:
<img width="320" height="200" alt="Image" src="https://github.com/user-attachments/assets/377e3f9d-0d25-4053-8d75-3f5afa8df619" />
<img width="320" height="200" alt="Image" src="https://github.com/user-attachments/assets/a635d296-6188-40b6-ad1f-8934809e109b" />

AROS upscaling is completely broken:
<img width="320" height="200" alt="Image" src="https://github.com/user-attachments/assets/1a8b34a8-23bc-4010-a07a-ae43e43fdf66" /><img width="320" height="200" alt="Image" src="https://github.com/user-attachments/assets/e56ced82-f46f-40d6-9a4a-7dde937a1eb5" />


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graphics: BitMapScale() broken for upscales, disagrees with OS3.x when downscaling #950

AmigaOS P96 8bpp

AROS amigavideo & Z3660

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graphics: BitMapScale() broken for upscales, disagrees with OS3.x when downscaling #950

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AmigaOS P96 8bpp

AROS amigavideo & Z3660

Metadata

Metadata

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Milestone

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Development

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