Refactor io.{h|cc} into other methods

[smadhuk]

With the removal of the IntermediateWeightedGraph, we can move all of the code from the io.* files into user_graph.* files. This also helps prepare the correlated-matching dev branch for upcoming changes where a new iter_dem_include_correlations method will depend on the UserEdge inside user_graph.h and prevent circular dependencies if the new method lived beside the currently existing iter method inside io.h.

This PR is a no-op on performance.

Before:

[.................*<<|....................] 530 us (vs 290 us) (2.8 Mdets/s) (9.6 Mlayers/s) (1.9 Mshots/s) Decode_surface_r5_d5_p1000
[................*<<<|....................]  23 ms (vs  10 ms) (920 kdets/s) ( 59 klayers/s) (5.3 kshots/s) Decode_surface_r11_d11_p100
[................*<<<|....................] 3.4 ms (vs 1.5 ms) (2.9 Mdets/s) (1.6 Mlayers/s) (140 kshots/s) Decode_surface_r11_d11_p1000
[..................*<|....................] 140 us (vs  83 us) (3.6 Mdets/s) ( 19 Mlayers/s) (1.8 Mshots/s) Decode_surface_r11_d11_p10000
[..................*<|....................]  56 us (vs  33 us) (3.3 Mdets/s) (190 Mlayers/s) ( 18 Mshots/s) Decode_surface_r11_d11_p100000
[................*<<<|....................]  16 ms (vs 7.5 ms) (600 kdets/s) (9.9 klayers/s) (470 shots/s) Decode_surface_r21_d21_p100
[...............*<<<<|....................]  22 ms (vs 7.8 ms) (450 kdets/s) (7.4 klayers/s) (350 shots/s) Decode_surface_r21_d21_p100_with_dijkstra
[................*<<<|....................]  23 ms (vs 8.2 ms) (440 kdets/s) (7.3 klayers/s) (340 shots/s) Decode_surface_r21_d21_p100_to_edges
[.................*<<|....................]  13 ms (vs 6.3 ms) (2.8 Mdets/s) (410 klayers/s) ( 19 kshots/s) Decode_surface_r21_d21_p1000
[...............*<<<<|....................]  26 ms (vs 7.7 ms) (1.3 Mdets/s) (200 klayers/s) (9.6 kshots/s) Decode_surface_r21_d21_p1000_with_dijkstra
[...............*<<<<|....................]  28 ms (vs 8.4 ms) (1.3 Mdets/s) (190 klayers/s) (9.0 kshots/s) Decode_surface_r21_d21_p1000_to_edges
[................*<<<|....................] 2.3 ms (vs 980 us) (3.2 Mdets/s) (4.5 Mlayers/s) (210 kshots/s) Decode_surface_r21_d21_p10000
[..............*<<<<<|....................] 4.8 ms (vs 1.3 ms) (1.6 Mdets/s) (2.2 Mlayers/s) (100 kshots/s) Decode_surface_r21_d21_p10000_with_dijkstra
[..............*<<<<<|....................] 6.0 ms (vs 1.4 ms) (1.2 Mdets/s) (1.7 Mlayers/s) ( 84 kshots/s) Decode_surface_r21_d21_p10000_to_edges
[.................*<<|....................] 180 us (vs  94 us) (3.9 Mdets/s) ( 58 Mlayers/s) (2.7 Mshots/s) Decode_surface_r21_d21_p100000
[...............*<<<<|....................] 400 us (vs 130 us) (1.8 Mdets/s) ( 26 Mlayers/s) (1.2 Mshots/s) Decode_surface_r21_d21_p100000_with_dijkstra
[...............*<<<<|....................] 420 us (vs 130 us) (1.7 Mdets/s) ( 25 Mlayers/s) (1.2 Mshots/s) Decode_surface_r21_d21_p100000_to_edges
[..................*<|....................]  54 ms (vs  35 ms) (180 loads/s) Load_dem_r11_d11_p100
[..................*<|....................] 440 ms (vs 280 ms) ( 22 loads/s) Load_dem_r21_d21_p100
[..................*<|....................]  54 ms (vs  35 ms) (180 loads/s) Load_dem_r11_d11_p100_correlations
[..................*<|....................] 430 ms (vs 280 ms) ( 23 loads/s) Load_dem_r21_d21_p100_correlations
[................*<<<|....................] 9.6 ms (vs 3.5 ms) (1.0 Gcalls/s) Varying32_get_distance_at_time
[..............*<<<<<|....................]  25 ms (vs 5.9 ms) (390 Mcalls/s) Varying64_get_distance_at_time
[....................*....................] 5.0 us (vs 4.9 us) (190 MEnqueueDequeues/s) bucket_queue_sort
[..................*<|....................] 140 us (vs  99 us) ( 67 MEnqueueDequeues/s) bucket_queue_stream

After:

[.................*<<|....................] 530 us (vs 290 us) (2.8 Mdets/s) (9.5 Mlayers/s) (1.9 Mshots/s) Decode_surface_r5_d5_p1000
[................*<<<|....................]  23 ms (vs  10 ms) (930 kdets/s) ( 59 klayers/s) (5.4 kshots/s) Decode_surface_r11_d11_p100
[................*<<<|....................] 3.4 ms (vs 1.5 ms) (2.9 Mdets/s) (1.6 Mlayers/s) (140 kshots/s) Decode_surface_r11_d11_p1000
[..................*<|....................] 140 us (vs  83 us) (3.6 Mdets/s) ( 19 Mlayers/s) (1.7 Mshots/s) Decode_surface_r11_d11_p10000
[..................*<|....................]  56 us (vs  33 us) (3.3 Mdets/s) (190 Mlayers/s) ( 18 Mshots/s) Decode_surface_r11_d11_p100000
[.................*<<|....................]  16 ms (vs 7.5 ms) (620 kdets/s) ( 10 klayers/s) (480 shots/s) Decode_surface_r21_d21_p100
[...............*<<<<|....................]  22 ms (vs 7.8 ms) (460 kdets/s) (7.5 klayers/s) (350 shots/s) Decode_surface_r21_d21_p100_with_dijkstra
[...............*<<<<|....................]  24 ms (vs 8.2 ms) (420 kdets/s) (6.9 klayers/s) (320 shots/s) Decode_surface_r21_d21_p100_to_edges
[.................*<<|....................]  13 ms (vs 6.3 ms) (2.8 Mdets/s) (410 klayers/s) ( 19 kshots/s) Decode_surface_r21_d21_p1000
[...............*<<<<|....................]  26 ms (vs 7.7 ms) (1.3 Mdets/s) (200 klayers/s) (9.5 kshots/s) Decode_surface_r21_d21_p1000_with_dijkstra
[...............*<<<<|....................]  27 ms (vs 8.4 ms) (1.3 Mdets/s) (190 klayers/s) (9.2 kshots/s) Decode_surface_r21_d21_p1000_to_edges
[................*<<<|....................] 2.3 ms (vs 980 us) (3.3 Mdets/s) (4.5 Mlayers/s) (210 kshots/s) Decode_surface_r21_d21_p10000
[..............*<<<<<|....................] 4.6 ms (vs 1.3 ms) (1.6 Mdets/s) (2.3 Mlayers/s) (110 kshots/s) Decode_surface_r21_d21_p10000_with_dijkstra
[...............*<<<<|....................] 4.9 ms (vs 1.4 ms) (1.5 Mdets/s) (2.1 Mlayers/s) (100 kshots/s) Decode_surface_r21_d21_p10000_to_edges
[.................*<<|....................] 180 us (vs  94 us) (4.0 Mdets/s) ( 59 Mlayers/s) (2.8 Mshots/s) Decode_surface_r21_d21_p100000
[...............*<<<<|....................] 400 us (vs 130 us) (1.8 Mdets/s) ( 26 Mlayers/s) (1.2 Mshots/s) Decode_surface_r21_d21_p100000_with_dijkstra
[...............*<<<<|....................] 420 us (vs 130 us) (1.7 Mdets/s) ( 25 Mlayers/s) (1.2 Mshots/s) Decode_surface_r21_d21_p100000_to_edges
[................*<<<|....................] 9.5 ms (vs 3.5 ms) (1.0 Gcalls/s) Varying32_get_distance_at_time
[..............*<<<<<|....................]  22 ms (vs 5.9 ms) (430 Mcalls/s) Varying64_get_distance_at_time
[....................*....................] 5.1 us (vs 4.9 us) (190 MEnqueueDequeues/s) bucket_queue_sort
[..................*<|....................] 140 us (vs  99 us) ( 67 MEnqueueDequeues/s) bucket_queue_stream

[oscarhiggott]

Nice!