bench: update random value generation

[hrshya]

Resolves none .

Description

What is the purpose of this pull request?

This pull request:

• Refactors random number generation in JS benchmarks for the math/base/special/round10, math/base/special/roundb, math/base/special/roundf and math/base/special/roundn packages.
• Replaces randu() with uniform() from @stdlib/random/array/uniform for cleaner and more consistent code.
• Moves the random number generation outside the benchmarking loops.
• Updates the test messages to follow code conventions.

Related Issues

Does this pull request have any related issues?

This pull request:

• resolves no related issues.

Questions

Any questions for reviewers of this pull request?

No.

Other

Any other information relevant to this pull request? This may include screenshots, references, and/or implementation notes.

No.

Checklist

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

• Read, understood, and followed the contributing guidelines.

---

@stdlib-js/reviewers

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
math/base/special/round10	$\color{green}216/216$ $\color{green}+100.00\%$	$\color{green}18/18$ $\color{green}+100.00\%$	$\color{green}2/2$ $\color{green}+100.00\%$	$\color{green}216/216$ $\color{green}+100.00\%$
math/base/special/roundb	$\color{green}203/203$ $\color{green}+100.00\%$	$\color{green}24/24$ $\color{green}+100.00\%$	$\color{green}2/2$ $\color{green}+100.00\%$	$\color{green}203/203$ $\color{green}+100.00\%$
math/base/special/roundf	$\color{green}258/258$ $\color{green}+100.00\%$	$\color{green}17/17$ $\color{green}+100.00\%$	$\color{green}2/2$ $\color{green}+100.00\%$	$\color{green}258/258$ $\color{green}+100.00\%$
math/base/special/roundn	$\color{green}279/279$ $\color{green}+100.00\%$	$\color{green}23/23$ $\color{green}+100.00\%$	$\color{green}2/2$ $\color{green}+100.00\%$	$\color{green}279/279$ $\color{green}+100.00\%$

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

[kgryte]

LGTM