feat: add stats/incr/nanmcv

[sagar7162]

Resolves #5568 .

Description

What is the purpose of this pull request?

This pull request:

• adds a new package nanmcv, that ignores NaN values.

Related Issues

Does this pull request have any related issues?

This pull request has the following related issues:

• [RFC]: add stats/incr/nanmcv #5568

Questions

Any questions for reviewers of this pull request?

No.

Other

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No.

Checklist

Please ensure the following tasks are completed before submitting this pull request.

• Read, understood, and followed the contributing guidelines.

AI Assistance

When authoring the changes proposed in this PR, did you use any kind of AI assistance?

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• No

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• Code generation (e.g., when writing an implementation or fixing a bug)
• Test/benchmark generation
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Disclosure

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{{TODO: add disclosure if applicable}}

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[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
stats/incr/nanmcv	$\color{green}148/148$ $color{green}+100.00%$	$\color{green}10/10$ $color{green}+100.00%$	$\color{green}2/2$ $color{green}+100.00%$	$\color{green}148/148$ $color{green}+100.00%$

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

[sagar7162]

@kgryte kindly review this PR.