GH-105848: Get rid of `KW_NAMES` by brandtbucher · Pull Request #105849 · python/cpython

It's not clear to me that it wouldn't be simpler to just do the conditional version with oparg flag right away in this PR (you've added a lot of PUSH_NULL that are going to be removed shortly, and I wouldn't want this intermediate state to persist without measuring the code size and perf impact), but since you've already done it this way, seems OK.

I originally benchmarked this and it was "0% faster", but I re-ran the benchmarks after merging in main and it came back 1% slower. So while it's probably in the noise, I agree it's probably just cleaner to do the oparg flag here since that is our end goal anyways, and it should make the perf impact less iffy.

I'll have some new commits with the flag up later today.