refactor: update stats/base/dnanmean native addon from C++ to C

[Neerajpathak07]

Resolves none

Description

What is the purpose of this pull request?

This pull request:

• updates the native addon from C++ to C

Related Issues

Does this pull request have any related issues?

This pull request:

• resolves none

Questions

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No.

Other

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Checklist

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• Read, understood, and followed the contributing guidelines

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[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
stats/base/dnanmean	$\color{green}359/359$ $\color{green}+100.00\%$	$\color{green}14/14$ $\color{green}+100.00\%$	$\color{green}4/4$ $\color{green}+100.00\%$	$\color{green}359/359$ $\color{green}+100.00\%$

The above coverage report was generated for the changes in this PR.

[Neerajpathak07]

@kgryte made the essential changes!!

[kgryte]

LGTM.