Super Metroid: Avoid unnecessary deep copies to improve generation speed.

[Zannick]

What is this fixing or adding?

Super Metroid's copy_mixin function showed up in profile results as 145s cumulative time, out of 639s (73 players). Most of that time is in deepcopy and my analysis showed the majority was spent copying the fields helpers and objectives, of which the latter breaks down further into goals and graph.

helpers just keeps a reference to the smbm, so we don't need to create another copy while we're copying, and graph is remarked as being something that doesn't change. As such, we can avoid making copies of those; helpers can point back at the new copy, and graph can be the same object.

Results:

• while profiling: 639s -> 412s (~36% improved)
• with spoiler=1: 213s -> 182s (~15% improved)
• with spoiler=3: 837s -> 742s (~11% improved)

@lordlou
Please note I did not confirm that the graph referenced by Objectives is not modified somewhere deeply hidden in the code, but since this did not break generation with the base settings I believe it works right.

How was this tested?

Generated with vs without this change on console with basic settings only, and compared spoiler logs. Did not try WebHost or map rando.