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/erfc, math/base/special/erfcinv, math/base/special/erfcx and math/base/special/erfinv 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-js/reviewers

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
math/base/special/erfc	$895/907$ $+98.68\mathrm{\%}$	$55/61$ $+90.16\mathrm{\%}$	$10/10$ $+100.00\mathrm{\%}$	$895/907$ $+98.68\mathrm{\%}$
math/base/special/erfcinv	$630/659$ $+95.60\mathrm{\%}$	$43/56$ $+76.79\mathrm{\%}$	$7/7$ $+100.00\mathrm{\%}$	$630/659$ $+95.60\mathrm{\%}$
math/base/special/erfcx	$1368/1443$ $+94.80\mathrm{\%}$	$95/95$ $+100.00\mathrm{\%}$	$79/104$ $+75.96\mathrm{\%}$	$1368/1443$ $+94.80\mathrm{\%}$
math/base/special/erfinv	$648/677$ $+95.72\mathrm{\%}$	$43/56$ $+76.79\mathrm{\%}$	$7/7$ $+100.00\mathrm{\%}$	$648/677$ $+95.72\mathrm{\%}$

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

[kgryte]

LGTM