Docs: Clarify/unify “stealing” docs

[encukou]

Documentation

For C functions that “steal” arguments:

• the behaviour on error should be explicitly mentioned for each function (see discussion);
• on top of that, the term “steal” deserves to be a glossary term that's linked from each use;
• the term always appears in quotes, see Poor terminology around reference ownership capi-workgroup/problems#11. (There's also a suggestion to avoid the term in prose entirely; that'll be out of scope for my PR.)

Linked PRs

• gh-144473: Add "steal" term to glossary; clarify "stealing" on error #144474
• gh-144473: Add "steal" term to glossary; clarify "stealing" on error #144502
• [3.15] gh-144473: Add "steal" term to glossary; clarify "stealing" on error (GH-144502) #152771
• [3.14] gh-144473: Add "steal" term to glossary; clarify "stealing" on error (GH-144502) #152772
• [3.13] gh-144473: Add "steal" term to glossary; clarify "stealing" onerror (GH-144502) (GH-152772) #152779

[serhiy-storchaka]

This term is only used in the C API documentation. It does not make sense in context of the Python language.