Make sure all sqlite3 doc examples work

[erlend-aasland]

Use Sphinx doctest features to ensure that all examples in the sqlite3 docs work as expected.

See also: https://diataxis.fr/tutorials/#ensure-that-the-tutorial-works-reliably

[erlend-aasland]

PR for the tutorial is up. I'll create a new PR for the rest later.

@CAM-Gerlach, @hugovk: does Sphinx support doctesting included files?

[CAM-Gerlach]

I actually know fairly little about docttests since I don't use them much myself (I primarily maintain docs for the Spyder-family GUI projects, where doctests aren't really relevant or practical), and most of what I know on Sphinx's support for them comes from reading the Sphinx documentation, which doesn't seem to mention this.

[erlend-aasland]

The literal includes are not tested. This is unfortunate. For sqlite3, I suggest inlining them; most of the snippets are very short. We can exploit this opportunity to make them even more succinct.

[erlend-aasland]

Fixed by:

• gh-95432: Add doctest for sqlite3 tutorial #96193
• [3.11] gh-95432: Add doctest for sqlite3 tutorial (GH-96193) #96200
• [3.10] gh-95432: Add doctest for sqlite3 tutorial (GH-96193) #96201
• gh-95432: Add doctests for the sqlite3 docs #96225
• [3.11] gh-95432: Add doctests for the sqlite3 docs (GH-96225) #96378
• [3.10] gh-95432: Add doctests for the sqlite3 docs (GH-96225) #96379