gh-137855: Improve import time of textwrap by lazy importing re modules

[XiaoWan-zi]

Summary

• Improve textwrap import time by lazy-importing re (PEP 810) instead of loading it at module import.
• Defer compilation of TextWrapper word-separator regexes from class body to _compile_wordseps(), called on first TextWrapper() instantiation. Compiled patterns remain class attributes, shared across instances (same semantics as before).
• Add LazyImportTest.test_lazy_import using ensure_lazy_imports() to guard against regressions.
  Part of the ongoing stdlib import-time work tracked in Improve import time of various stdlib modules #137855.

Motivation

textwrap is imported eagerly by many modules (e.g. tests, traceback, optparse paths) often only for dedent() / indent(), which do not need re. Previously, import re at module level and re.compile() in the TextWrapper class body caused re to load on every import textwrap.

Before

After

[picnixz]

This is a nontrivial change that may break subclasses so closing, sorry.

[bedevere-app]

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