feat: add benchmarks for spergel profile

[beckermr]

This PR adds a benchmark for the Spergel profile. I can indeed confirm it is a few times slower than galsim on the CPU.

xref: #123

[codspeed-hq]

CodSpeed Performance Report

Merging #125 will not alter performance

_{Comparing spergel-bench (49872d8) with main (1e270c4)}

Summary

✅ 11 untouched benchmarks
🆕 6 new benchmarks

Benchmarks breakdown

	Benchmark	main	spergel-bench	Change
🆕	test_benchmark_spergel_conv[compile]	N/A	3.3 s	N/A
🆕	test_benchmark_spergel_conv[run]	N/A	2.6 s	N/A
🆕	test_benchmark_spergel_kvalue[compile]	N/A	698.2 ms	N/A
🆕	test_benchmark_spergel_kvalue[run]	N/A	137.2 ms	N/A
🆕	test_benchmark_spergel_xvalue[compile]	N/A	27.7 s	N/A
🆕	test_benchmark_spergel_xvalue[run]	N/A	24.5 s	N/A

[ismael-mendoza]

Thanks @beckermr this looks good to me! Perhaps consider adding a benchmark with the HLR liked we talked about?