Instead of using a struct member to hold the last barrel shifter carry output, which is expansive as it needs to be saved/loaded from memory, I now pass the carry around as an INOUT parameter.
Using perf anotate really shows high perctile of samples being spent on reading/writing `self.bs_carry_out`
Since this is a rather "surgical" changeset, I have made sure to run it against eggvance test suite, mGBA test suite and some games as well.
I actually saw better improvements than what the benchmark measured, but 7% is decent enough :)
```
run_60_frames time: [180.18 ms 180.45 ms 180.77 ms]
change: [-7.2464% -6.9081% -6.6324%] (p = 0.00 < 0.05)
Performance has improved.
```
Former-commit-id: 7cd7105a07aa0b78cab9dc8bbae3682b02b7ab7c
Former-commit-id: c68514beb3fa6c34f5f65544acbead21e527dbb0
