bench: refactor random number generation in stats/base/dists/signrank

[AryanJ18]

bench:refactor random number generation in stats/base/dists/signrank issue: #4986

Resolves #4986 .

Description

What is the purpose of this pull request?

This pull request:

This pull request improves random number generation in JS benchmarks for stats/base/dists/signrank. Specifically:
Moves random number generation out of benchmarking loops to prevent interference with benchmark results.
Uses @stdlib/random/base/uniform and @stdlib/random/base/discrete-uniform instead of randu expressions.
Ensures generated random values maintain the same range as existing values for consistency.

Related Issues

Does this pull request have any related issues?

This pull request has the following related issues:

References #4837 and #4955 as examples of similar improvements.

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.

AI Assistance

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• No

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• Test/benchmark generation
• Documentation (including examples)
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{{TODO: add disclosure if applicable}}

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Coverage Report

Package	Statements	Branches	Functions	Lines
stats/base/dists/signrank/cdf	$\color{red}309/311$ $\color{green}+0.00%$	$\color{red}36/37$ $\color{green}+0.00%$	$\color{green}4/4$ $\color{green}+0.00%$	$\color{red}309/311$ $\color{green}+0.00%$
stats/base/dists/signrank/quantile	$\color{green}305/305$ $\color{green}+0.00%$	$\color{green}45/45$ $\color{green}+0.00%$	$\color{green}4/4$ $\color{green}+0.00%$	$\color{green}305/305$ $\color{green}+0.00%$

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