Implement setattr builtin function

[friendlymatthew]

This PR implements the setattr function for dynamic attribute modification on objects. The implementation uses the existing py_set_attr infrastructure

Note: the docs state this method is the counterpart of #65

[codspeed-hq]

Merging this PR will not alter performance

✅ 11 untouched benchmarks

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_{Comparing setattr (dab2920) with main (7909646)}