gh-118761: Improve import time for csv

[picnixz]

Benchmarks are for a release non-PGO build (PR) against a PGO build (main). This will be the last PR for that issue.

Note

Considering that csv is used in many applications, I think this improvement makes sense (especially for data scientists).

PR

$ ./python -X importtime -c 'import csv'
import time: self [us] | cumulative | imported package
...
import time:       229 |        229 | linecache
import time:       331 |        331 |   types
import time:       175 |        175 |   _csv
import time:       629 |       1134 | csv

$ hyperfine --warmup 8 "./python -c 'import csv'"
Benchmark 1: ./python -c 'import csv'
  Time (mean ± σ):       5.9 ms ±   0.4 ms    [User: 5.0 ms, System: 1.0 ms]
  Range (min … max):     5.5 ms …  11.0 ms    452 runs

Main

$ ./python -X importtime -c 'import csv'
import time: self [us] | cumulative | imported package
...
import time:       227 |        227 | linecache
import time:       261 |        261 |       types
import time:      1419 |       1680 |     enum
import time:        62 |         62 |       _sre
import time:       218 |        218 |         re._constants
import time:       327 |        544 |       re._parser
import time:        79 |         79 |       re._casefix
import time:       287 |        971 |     re._compiler
import time:        90 |         90 |         itertools
import time:        86 |         86 |         keyword
import time:        46 |         46 |           _operator
import time:       187 |        233 |         operator
import time:       119 |        119 |         reprlib
import time:        45 |         45 |         _collections
import time:       733 |       1304 |       collections
import time:        39 |         39 |       _functools
import time:       498 |       1840 |     functools
import time:       114 |        114 |     copyreg
import time:       426 |       5029 |   re
import time:       107 |        107 |   _csv
import time:       575 |       5709 | csv

$ hyperfine --warmup 8 "./python -c 'import csv'"
Benchmark 1: ./python -c 'import csv'
  Time (mean ± σ):       9.2 ms ±   0.9 ms    [User: 8.0 ms, System: 1.2 ms]
  Range (min … max):     8.4 ms …  16.7 ms    297 runs

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

[vstinner]

LGTM

[picnixz]

In a few hours, I will leave until Friday, but I'd like Adam or Hugo to review my English. Feel free to merge this PR and freely update it (otherwise, I'll do it once I'm back).

[hugovk]

Looks good, thanks!