Fix a bug in extract_single_sample

[jeremykubica]

Make a quick fix to the copy and extract_single_sample function in GraphState. These were not copying over the fixed_var and the sample_offset information. This isn't used anywhere (yet), so it hasn't been causing a problem. But was causing a failure for some of the bagle tests.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.60%. Comparing base (6f72ab8) to head (8650f8d).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #626   +/-   ##
=======================================
  Coverage   94.60%   94.60%           
=======================================
  Files          62       62           
  Lines        5426     5431    +5     
=======================================
+ Hits         5133     5138    +5     
  Misses        293      293           

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[github-actions]

Before [6f72ab8]	After [1974c84]	Ratio	Benchmark (Parameter)
27.2±0.2ms	43.9±0.4ms	1.62	benchmarks.TimeSuite.time_make_and_evaluate_static_sed
48.6±0.4ms	75.2±1ms	1.55	benchmarks.TimeSuite.time_additive_multi_model_source
18.3±0.2ms	27.0±0.5ms	1.47	benchmarks.TimeSuite.time_make_evaluate_constant_sed_model
5.24±0.07ms	6.94±0.1ms	1.32	benchmarks.TimeSuite.time_lightcurve_source
737±20μs	772±40μs	1.05	benchmarks.TimeSuite.time_fnu_to_flam
100±2μs	104±2μs	1.03	benchmarks.TimeSuite.time_make_and_evaluate_step_model
1.02±0.01s	1.05±0.01s	1.03	benchmarks.TimeSuite.time_make_x1_from_hostmass
130±4μs	132±5μs	1.02	benchmarks.TimeSuite.time_evaluate_simple_linear_wavelength_model
4.52±0.1ms	4.54±0.06ms	1.01	benchmarks.TimeSuite.time_evaluate_salt3_passbands
105±2μs	106±2μs	1.01	benchmarks.TimeSuite.time_sample_x0_from_distmod

Click here to view all benchmarks.