Use plf linked list impl for shadowcasting

[ifreund]

Summary

SUMMARY: Performance "Use plf linked list impl for shadowcasting."

Purpose of change

This linked list implementation has better performance characteristics than the standard library implementation and gives us a slight speedup for shadowcasting, where we can use all the performance we can get.

This is the last step towards resolving #6821 now that my and kevin's work in #32012 and #42835 has been merged. Further iteration on the 3d shadowcasting algorithm may be split into more specific issues, the core of the implementation is sound.

Closes #6821

Testing

Ran the test suite locally, tested in game without any noticeable bugs.

[kevingranade]

Just out of curiosity, can you run tests/cata_test "shadowcasting_3d_2d_performance" on the before and after of this?
You probably want to open up tests/shadowcasting_test.cpp and knock a 0 off the iteration count of the benchmark, on my test system it was running for 30 minutes :/

[ifreund]

I got:

before: cast_zlight() executed 100000 times in 757991174 microseconds. 
after: cast_zlight() executed 100000 times in 695576696 microseconds.

I also played around with naively splitting up the cast zlight_segment calls into multiple threads which didn't seem to immediately break things, could use more investigation.