feat: add C ndarray interface and refactor implementation for stats/base/svariancewd

[aayush0325]

Description

What is the purpose of this pull request?

This pull request:

• adds C ndarray interface for stats/base/svariancewd
• refactors JavaScript implementation
• updates tests, docs, examples and benchmarks

Related Issues

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No.

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No.

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Checklist

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• Read, understood, and followed the contributing guidelines.

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@stdlib-js/reviewers

[aayush0325]

for the reviewer: We need to address the representation of the correction parameter as a double using decimals in this PR, do we only need that in the README and typescript declaration file or in tests, benchmarks JSDoc etc as well?

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
stats/base/svariancewd	$\color{green}452/452$ $\color{green}+100.00\%$	$\color{green}21/21$ $\color{green}+100.00\%$	$\color{green}4/4$ $\color{green}+100.00\%$	$\color{green}452/452$ $\color{green}+100.00\%$

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