feat: add benchmark for gradient w/ moffat

[beckermr]

This PR adds a benchmark for a grad of conv for a moffat profile.

[codspeed-hq]

Merging this PR will not alter performance

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

✅ 34 untouched benchmarks
🆕 2 new benchmarks

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
🆕	Simulation	test_benchmark_moffat_conv_grad[run]	N/A	13.6 s	N/A
🆕	WallTime	test_benchmark_moffat_conv_grad[run]	N/A	1.4 s	N/A

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_{Comparing moffat-grad-bench (cfe7764) with main (c0c4e3a)}