Fix memory bugs in the PBC passes

[dime10]

Primarily, iterator invalidation (mutation while iterating). Also one instance of using an object after deletion.
These issues are hard to surface through unit testing, but are reported by the address sanitizer.

[github-actions]

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[paul0403]

Ah, the classic!

[lazypanda10117]

Thanks @dime10!

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.90%. Comparing base (6ace49f) to head (f22dfd2).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2918      +/-   ##
==========================================
- Coverage   96.90%   96.90%   -0.01%     
==========================================
  Files         166      166              
  Lines       19012    19008       -4     
  Branches     1760     1760              
==========================================
- Hits        18424    18420       -4     
  Misses        433      433              
  Partials      155      155              

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