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 stats/base/dists/chi/* packages.
• Replaces 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.

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[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
stats/base/dists/chi/cdf	$\color{red}214/216$ $\color{green}+99.07\%$	$\color{red}21/22$ $\color{green}+95.45\%$	$\color{green}3/3$ $\color{green}+100.00\%$	$\color{red}214/216$ $\color{green}+99.07\%$
stats/base/dists/chi/ctor	$\color{green}387/387$ $\color{green}+100.00\%$	$\color{green}25/25$ $\color{green}+100.00\%$	$\color{green}14/14$ $\color{green}+100.00\%$	$\color{green}387/387$ $\color{green}+100.00\%$
stats/base/dists/chi/entropy	$\color{green}166/166$ $\color{green}+100.00\%$	$\color{green}8/8$ $\color{green}+100.00\%$	$\color{green}2/2$ $\color{green}+100.00\%$	$\color{green}166/166$ $\color{green}+100.00\%$
stats/base/dists/chi/kurtosis	$\color{green}115/115$ $\color{green}+100.00\%$	$\color{green}6/6$ $\color{green}+100.00\%$	$\color{green}1/1$ $\color{green}+100.00\%$	$\color{green}115/115$ $\color{green}+100.00\%$
stats/base/dists/chi/logpdf	$\color{green}239/239$ $\color{green}+100.00\%$	$\color{green}27/27$ $\color{green}+100.00\%$	$\color{green}3/3$ $\color{green}+100.00\%$	$\color{green}239/239$ $\color{green}+100.00\%$
stats/base/dists/chi/mean	$\color{green}163/163$ $\color{green}+100.00\%$	$\color{green}8/8$ $\color{green}+100.00\%$	$\color{green}2/2$ $\color{green}+100.00\%$	$\color{green}163/163$ $\color{green}+100.00\%$

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

[kgryte]

LGTM. Thanks, @hrshya!