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

[gururaj1512]

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• task: lint_filenames status: passed
• task: lint_editorconfig status: passed
• task: lint_markdown status: passed
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• task: lint_javascript_src status: passed
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• task: lint_c_src status: missing_dependencies
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Resolves None

Description

What is the purpose of this pull request?

This pull request:

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

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• None

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• Read, understood, and followed the contributing guidelines.

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Coverage Report

Package	Statements	Branches	Functions	Lines
stats/base/snanvariancepn	$\color{green}603/603$ $\color{green}+100.00\%$	$\color{green}45/45$ $\color{green}+100.00\%$	$\color{green}5/5$ $\color{green}+100.00\%$	$\color{green}603/603$ $\color{green}+100.00\%$

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

[kgryte]

@gururaj1512 Rather than make these changes to this internal function, why not just go ahead and add the package blas/ext/base/snannsumpw in a separate PR and then use that API here after it is merged? While the changes here are okay, they are just going to get thrown away once we have snannsumpw. This is what we already do in dnanvariancepn and would be good to follow a similar approach here.

[kgryte]

Other than the need for blas/ext/base/snannsumpw, this PR is looking good after some minor clean-up.