bench: replace stack allocation with dynamic allocation

[navyansh007]

fix(math/strided/special/dfloor): replace stack allocation with dynamic allocation in benchmark

Replace fixed-size array declarations with dynamic memory allocation in
the dfloor benchmark to prevent segmentation faults when processing
large input sizes. The benchmark previously failed with segmentation
faults for arrays with 1,000,000 elements due to stack memory limitations.

Changes:

• Replace stack-allocated arrays with malloc/free for x and y arrays
• Add proper error handling for memory allocation failures
• Add memory cleanup to prevent memory leaks
• Add error checking in main benchmark loop

Fixes: #7224

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Coverage Report

Package	Statements	Branches	Functions	Lines
math/strided/special/dfloor	$\color{green}374/374$ $\color{green}+100.00\%$	$\color{green}15/15$ $\color{green}+100.00\%$	$\color{green}4/4$ $\color{green}+100.00\%$	$\color{green}374/374$ $\color{green}+100.00\%$

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