Remove unused imports from the stdlib

[vstinner]

Using pyflakes or ruff, I found unused imports and I created this issue to remove them.

Linked PRs

• gh-120417: Remove unused imports in the stdlib #120420
• gh-120417: Add #noqa to used imports in the stdlib #120421
• [3.13] gh-120417: Remove unused imports in the stdlib (GH-120420) #120429
• gh-120417: Add more #noqa to used imports in the stdlib #120454
• gh-120417: Fix "imported but unused" linter warnings #120461
• [3.12] gh-120417: Remove unused import in idlelib (GH-120420) #120574
• gh-120417: Remove unused imports in cases_generator #120622
• gh-120417: Remove unused imports in Tools #120623
• gh-120417: Add #noqa to load_tests() in tests #120626
• gh-120417: Add #noqa: F401 to tests #120627
• gh-120417: Modify test_bdb to use the import #120628
• gh-120417: Remove unused imports in tests (part 1) #120629
• gh-120417: Remove unused imports in tests (part 2) #120630
• gh-120417: Remove unused imports in tests (part 3) #120631
• gh-120417: Remove unused imports in tests (part 4) #120632
• gh-120417: Move imports to doctests in test_doctest #120679
• gh-120417: Use import_helper() in test_regrtest #120680