Define "standard library" and "stdlib" in the glossary

[zware]

Documentation

As suggested by @JulienPalard in response to @adorilson's question in https://discuss.python.org/t/what-means-stdlib/97201/6

PR incoming for bikeshedding :)

Linked PRs

• gh-136145: Define 'standard library' and 'stdlib' in the glossary #136146
• [3.14] gh-136145: Define 'standard library' and 'stdlib' in the glossary (GH-136146) #136485
• [3.13] gh-136145: Define 'standard library' and 'stdlib' in the glossary (GH-136146) #136486