Add more tests for correlated decoding and fix undo_reweights on search graph (#169)

* Add more exhaustive tests of correlations. Fix a bug where edge weight rewrites in the search graph weren't always undone.

* remove graph structure comparison method from MatchingGraph

* update correlated matching test data

Author: oscarhiggott

…dictions_pymatchingv2.2.2_correlated.txt …ts_predictions_pymatching_correlated.txtdata/surface_code_rotated_memory_x_13_0.01_1000_shots_no_buckets_predictions_pymatchingv2.2.2_correlated.txt renamed to data/surface_code_rotated_memory_x_13_0.01_1000_shots_no_buckets_predictions_pymatching_correlated.txt data/surface_code_rotated_memory_x_13_0.01_1000_shots_no_buckets_predictions_pymatchingv2.2.2_correlated.txt renamed to data/surface_code_rotated_memory_x_13_0.01_1000_shots_no_buckets_predictions_pymatching_correlated.txt

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