perf: make test suite snappier and clean up some testing things

[beckermr]

This PR makes the test suite snappier by:

• using pytest-split to split the tests over four jobs
• removing extra benchmarks

I've also fixed a few deprecations, bugs, and minor oddities in the tests to make life easier. This includes

• updating the pre-commit hooks to use the correct hook for ruff-check
• changed codspeed mode to simulation to match latest API
• changing imports in the tests to allow them to be run without import errors due to not having galsim's test utils module
• adding a call to make the output directory in our text fixture if it does not exist
• removed premade output directory in favor of making it on the fly

closes #166

[codspeed-hq]

Merging this PR will improve performance by 35.48%

⚡ 1 improved benchmark
✅ 15 untouched benchmarks

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Simulation	test_benchmark_spergel_calcfluxrad[run]	1.5 ms	1.1 ms	+35.48%

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_{Comparing parallel-tests (eb21f94) with main (cfa1bfd)}