Case insensitivity of sheet, column, and setting names; plus more performance improvements#746

Draft

lindsay-stevens wants to merge 11 commits intoXLSForm:masterfrom lindsay-stevens:pyxform-738

+1,965-1,365

Commits on Jan 2, 2025

chg: tidy choices module, minor xls2json improvements
lindsay-stevens
committed

Commits on Jan 3, 2025

chg: make sheet column headers case-insensitive
lindsay-stevens
committed
dev: use slots on all dataclasses for reduced memory usage
lindsay-stevens
committed
chg: make all xls2json backends emit a structured type with headers
lindsay-stevens
committed

Commits on Jan 7, 2025