Add SN Ia efficiency functions

[mi-dai]

Add functions to calculate photometric detection efficiency and spectroscopic follow-up efficiency. Actual implementation in the pipeline will be next step.

[github-actions]

Before [88bd226]	After [d59a0f1]	Ratio	Benchmark (Parameter)
4.30±1ms	4.41±0.2ms	1.03	benchmarks.TimeSuite.time_chained_evaluate
9.46±1ms	9.78±1ms	1.03	benchmarks.TimeSuite.time_evaluate_salt3_model
5.20±0.4ms	5.28±0.2ms	1.02	benchmarks.TimeSuite.time_evaluate_salt3_passbands
1.41±0.07ms	1.41±0.09ms	1	benchmarks.TimeSuite.time_apply_passbands
15.6±0.2μs	15.5±0.5μs	1	benchmarks.TimeSuite.time_sample_x1_from_hostmass
1.99±1ms	1.97±1ms	0.99	benchmarks.TimeSuite.time_fnu_to_flam
8.96±0.08ms	8.87±0.05ms	0.99	benchmarks.TimeSuite.time_load_passbands
27.8±0.3μs	27.3±0.1μs	0.99	benchmarks.TimeSuite.time_make_new_salt3_model
1.35±0.01s	1.33±0.01s	0.98	benchmarks.TimeSuite.time_make_x1_from_hostmass
122±3μs	119±1μs	0.98	benchmarks.TimeSuite.time_sample_x0_from_distmod

Click here to view all benchmarks.

[OliviaLynn]

Looks good! Just want to check that test_obs_utils.py is intentionally left blank, however--is this a placeholder?

[mi-dai]

Whoops, I meant to write tests but just somehow forgot about it! Will do it in another PR. Thanks for catching it!

[mi-dai]

@OliviaLynn I added tests here. Could you take another look?