Provide ability to use a default search radius for the OpSim

[jeremykubica]

Allow a default search radius so we can pass all the information needed for spatial matching together in a single OpSim object.

[github-actions]

Before [080d28c]	After [530644a]	Ratio	Benchmark (Parameter)
6.46±0.8ms	5.05±0.8ms	~0.78	benchmarks.TimeSuite.time_chained_evaluate
1.88±0.6ms	1.02±0.5ms	~0.54	benchmarks.TimeSuite.time_fnu_to_flam
1.40±0.06ms	1.46±0.04ms	1.04	benchmarks.TimeSuite.time_apply_passbands
9.86±0.2ms	9.99±0.3ms	1.01	benchmarks.TimeSuite.time_evaluate_salt3_model
4.98±0.1ms	4.99±0.2ms	1.00	benchmarks.TimeSuite.time_evaluate_salt3_passbands
8.75±0.06ms	8.71±0.09ms	1.00	benchmarks.TimeSuite.time_load_passbands
28.2±0.2μs	28.0±0.2μs	0.99	benchmarks.TimeSuite.time_make_new_salt3_model
130±2μs	128±1μs	0.98	benchmarks.TimeSuite.time_sample_x0_from_distmod
16.4±0.3μs	16.2±0.2μs	0.98	benchmarks.TimeSuite.time_sample_x1_from_hostmass
1.40±0.01s	1.36±0.01s	0.97	benchmarks.TimeSuite.time_make_x1_from_hostmass

Click here to view all benchmarks.

[hombit]

Thank you