sqlite3 docs: extract row factory examples into row factory howto

[erlend-aasland]

There are several row factory examples scattered around the sqlite3 docs. Most of them in various places in the reference. Suggesting to extract them and create a row factory How-to Guide, in order to clean up the reference and reduce duplication of information.

• gh-96168: Improve sqlite3 dict_factory example #96457

• [3.11] gh-96168: Improve sqlite3 dict_factory example (GH-96457) #96494

• [3.10] gh-96168: Improve sqlite3 dict_factory example (GH-96457) #96495

• gh-96168: Add sqlite3 row factory how-to #99507

• [3.11] gh-96168: Add sqlite3 row factory how-to (GH-99507) #99778

• [3.10] gh-96168: Add sqlite3 row factory how-to (GH-99507) #99779

[erlend-aasland]

cc. @CAM-Gerlach @ezio-melotti

[CAM-Gerlach]

Seems reasonable to me—short-ish examples are reasonable for a reference, but advice like

If returning a tuple doesn’t suffice and you want name-based access to columns, you should consider setting row_factory to the highly optimized sqlite3.Row type. Row provides both index-based and case-insensitive name-based access to columns with almost no memory overhead. It will probably be better than your own custom dictionary-based approach or even a db_row based solution.

is much more appropriate in a how-to, or perhaps actually an explanation (but there isn't really enough meat for that, and a how-to is certainly closer than a reference here)

[erlend-aasland]

As a first step, I suggest to improve the dict-factory example by:

• modernising the code; we can use a dict comprehension
• using a doctest, so the expected output is visible
• SELECTing a row with multiple columns, so the effect of the dict factory becomes clearer