Function parse 

pub fn parse(s: &str) -> ParamList

Parse a proj-string into an ordered ParamList.

First normalizes the string with shrink (PROJ pj_shrink: collapse whitespace, make =/, greedy), then splits on ASCII whitespace, strips one leading + per token, and splits each token on the first =. Bare tokens become (key, None). Cannot fail.

Ported from src/param.cpp (argument tokenization) plus src/internal.cpp (pj_shrink).