gh-118761: Improve import time of sqlite3

[Wulian233]

Improve import time of sqlite3 by around 2 times

Benchmark on Windows10, Python official 3.13.1

D:\Python313>hyperfine --warmup 8 "./python -c 'from sqlite3 import *'" "./python -c 'from sqlite3_new import *'"
Benchmark 1: ./python -c 'from sqlite3 import *'
  Time (mean ± σ):     135.0 µs ± 174.7 µs    [User: 1743.5 µs, System: 2196.8 µs]
  Range (min … max):     0.0 µs … 1225.1 µs    404 runs

Benchmark 2: ./python -c 'from sqlite3_new import *'
  Time (mean ± σ):     153.7 µs ± 196.7 µs    [User: 1868.9 µs, System: 1971.3 µs]
  Range (min … max):     0.0 µs … 2125.8 µs    409 runs

Summary
  ./python -c 'from sqlite3 import *' ran
    1.14 ± 2.07 times faster than ./python -c 'from sqlite3_new import *'

Outdated file comments have also been updated

• Issue: Improve import time of various stdlib modules #118761

[erlend-aasland]

Please leave out all unrelated comment changes.

[Wulian233]

@erlend-aasland Thanks review! I have removed unrelated comments, and correcting outdated information was retained. Changed in 3.13

https://github.com/python/cpython/blob/main/Doc%2Fusing%2Fconfigure.rst#L59-L59