bench: refactor to use dynamic memory allocation in number/uint8/base/mul

[piyxsh31]

Resolves a part of #8643.

Description

What is the purpose of this pull request?

This pull request:

• replace static memory allocation of large arrays in C benchmark at number/uint8/base/mul with dynamic memory allocation (tracking issue)

Related Issues

Does this pull request have any related issues?

This pull request has the following related issues:

• [RFC]: replace static memory allocation of large arrays in C benchmarks with dynamic memory allocation (tracking issue) #8643

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No.

Other

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• Read, understood, and followed the contributing guidelines.

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{{TODO: add disclosure if applicable}}

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[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
number/uint8/base/mul	$\color{green}157/157$ $\color{green}+100.00%$	$\color{green}5/5$ $\color{green}+100.00%$	$\color{green}2/2$ $\color{green}+100.00%$	$\color{green}157/157$ $\color{green}+100.00%$

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

[kgryte]

Ref: #9229 (comment)