Fill mean and stdDev tails with zeros for HAL branch in meanStdDev opencv#25789

as it's done for other branches.

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… on ARM.

Added flag to GaussianBlur for faster but not bit-exact implementation opencv#25792

Rationale:
Current implementation of GaussianBlur is almost always bit-exact. It helps to get predictable results according platforms, but prohibits most of approximations and optimization tricks.

The patch converts `borderType` parameter to more generic `flags` and introduces `GAUSS_ALLOW_APPROXIMATIONS` flag to allow not bit-exact implementation. With the flag IPP and generic HAL implementation are called first. The flag naming and location is a subject for discussion.

Replaces opencv#22073
Possibly related issue: opencv#24135

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HAL for dot product added opencv#25936

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pyrDown: offset HAL added, IPP removed opencv#25970

Resolves opencv#25976

### Changes
* HAL added for offset support so that border pixels can be fetched from outside of the image ROI (see `BORDER_ISOLATED` parameter)
* IPP removed since there is `pyrUp` instead of `pyrDown` and there's no easy way to fix this other than rewriting it from scratch
* replaced old C call by modern `cv::pyrDown`

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…ffset

Added offset for HAL as ofs2idx expects 1-based index opencv#26080

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Added HAL interface for Lukas-Kanade optical flow opencv#26143

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HAL interface for Sharr derivatives needed for Lukas-Kanade algorithm opencv#26163

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Added Fastcv HAL changes in the 3rdparty folder.
Includes HAL code , Fastcv libs and Headers

Change-Id: I2f0ddb1f57515c82ae86ba8c2a82965b1a9626ec

Reorganized the files in the folder,
Added rules to download the fastcv bins
from the 3rdparty repo

Change-Id: Ia66f138894d3e8a06d0f32a6e7ce3359619189d7