gh-106751: Optimize KqueueSelector.select() for many iteration case

[corona10]

• Issue: Optimize XXXSelector for many iterations of the event loop #106751

[corona10]

Similar technique can be adopted.

Benchmark

import timeit
import os
from selectors import KqueueSelector, EVENT_WRITE, EVENT_READ

kqueue = KqueueSelector()
for _ in range(100):
    r, w = os.pipe()
    os.write(w, b"a")
    kqueue.register(r, EVENT_READ)

elapsed = timeit.timeit(
    "selector.select()",
    number=100000,
    globals={"selector": kqueue},
)

print(f"elapsed: {elapsed}")

Result

AS-IS: elapsed -> 2.3957692080002744
TO-BE: elapsed -> 2.2462058329983847 (1.06x faster)

[eendebakpt]

A minor suggestion. Otherwise looks good.

[bdraco]

Awesome. Thanks for picking up the other ones!