gh-62172: Document classify_class_attrs(), getabsfile(), and indentsize() in inspect

[sreehariannam]

Adds documentation for three public, __all__-exported functions in the inspect module that were missing from Doc/library/inspect.rst:

• inspect.getabsfile()
• inspect.indentsize()
• inspect.classify_class_attrs()

Towards gh-62172. That issue lists several other undocumented functions (findsource, getblock, walktree, getargs, formatannotation, formatannotationrelativeto, getlineno) which are left for a follow-up PR to keep this change small and reviewable.

Verified with sphinx-lint (no issues) against the current Doc/library/inspect.rst.

[python-cla-bot]

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[read-the-docs-community]

Documentation build overview

📚 cpython-previews | 🛠️ Build #33552363 | 📁 Comparing 607db18 against main (dd2faeb)

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2 files changed

± library/inspect.html
± whatsnew/changelog.html

[sreehariannam]

Thanks for the review! Addressed both points in the latest commit: dropped the normcase implementation detail from getabsfile's description, and linked named tuple via :term: in classify_class_attrs.