refactor: use stdlib_base_round instead of builtin in math/base/special/cround

[gunjjoshi]

Description

What is the purpose of this pull request?

This pull request:

• Completes the TODO to use stdlib_base_round instead of builtin in the C implementation of math/base/special/cround.
• updates C benchmarks to follow latest conventions.

Related Issues

Does this pull request have any related issues?

None.

Questions

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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.

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@stdlib-js/reviewers

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
math/base/special/cround	$\color{green}219/219$ $\color{green}+100.00\%$	$\color{green}5/5$ $\color{green}+100.00\%$	$\color{green}2/2$ $\color{green}+100.00\%$	$\color{green}219/219$ $\color{green}+100.00\%$

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

[kgryte]

LGTM. Thanks, @gunjjoshi!