Improve efficiency of ObsTableUniformRADECSampler

[jeremykubica]

Improve the efficiency of the ObsTableUniformRADECSampler by only testing the newly generated points (instead of checking everything, including the previously valid points). This does not fix the problems we occasionally see with the samples being out of bounds. But it makes debugging more efficient.

Also increase the coverage of the tests.

[github-actions]

Before [ae17725]	After [576a549]	Ratio	Benchmark (Parameter)
46.5±0.3μs	48.6±0.8μs	1.04	benchmarks.TimeSuite.time_make_new_salt3_model
29.1±0.3μs	30.1±0.5μs	1.04	benchmarks.TimeSuite.time_make_simple_linear_wavelength_model
672±10μs	695±20μs	1.03	benchmarks.TimeSuite.time_fnu_to_flam
9.36±0.3ms	9.55±0.3ms	1.02	benchmarks.TimeSuite.time_evaluate_salt3_model
4.80±0.1ms	4.89±0.09ms	1.02	benchmarks.TimeSuite.time_lightcurve_source
12.8±0.09μs	13.1±0.2μs	1.02	benchmarks.TimeSuite.time_sample_x1_from_hostmass
19.1±0.2ms	19.2±0.3ms	1.01	benchmarks.TimeSuite.time_chained_evaluate_sed
34.2±0.4ms	34.3±0.09ms	1	benchmarks.TimeSuite.time_additive_multi_model_source
554±9μs	556±9μs	1	benchmarks.TimeSuite.time_apply_passbands
7.58±0.1ms	7.55±0.05ms	1	benchmarks.TimeSuite.time_apply_white_noise

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