Switch to rust implementation of calcrom

[PikalaxALT]

PR checklist

• This comment contains a description of changes (with reason).
• The ROM compiles to matching locally (make compare_heartgold && make compare_soulsilver).
• All C code is correctly formatted (git clang-format).
• This pull request is labeled according to the kind of work it represents.
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[adrienntindall]

Gonna trust this works since I don't see anything obviously wrong, but we won't know for sure until it's merged anyway.