Inifix

PERF: optimize parsing speed (reduce reading overhead by an additional 5%)

BUG: fix a regression (in 4.2.0) where signed floats were interpreted as strings

PERF: optimize parsing speed (reduce reading overhead by 60%)

- ENH: allow skipping validation in IO operations
- ENH: allow special character '.' in parameter names

TST: use requirement files instead of optional dependencies for tests and type checking

Installing with extra targets (`[test]` and `[typecheck]`) isn't supported anymore.

- ENH: optimize startup time
- ENH: add option to load scalars as single-element lists