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/exp, math/base/special/exp10 and math/base/special/expit 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

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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-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
math/base/special/exp	$\color{red}481/487$ $\color{green}+98.77\%$	$\color{red}21/24$ $\color{green}+87.50\%$	$\color{green}4/4$ $\color{green}+100.00\%$	$\color{red}481/487$ $\color{green}+98.77\%$
math/base/special/exp10	$\color{green}330/330$ $\color{green}+100.00\%$	$\color{green}19/19$ $\color{green}+100.00\%$	$\color{green}4/4$ $\color{green}+100.00\%$	$\color{green}330/330$ $\color{green}+100.00\%$
math/base/special/expit	$\color{green}179/179$ $\color{green}+100.00\%$	$\color{green}7/7$ $\color{green}+100.00\%$	$\color{green}2/2$ $\color{green}+100.00\%$	$\color{green}179/179$ $\color{green}+100.00\%$

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