`normalize_identifier` is called quite often in the generator, once for every variable name or path element that is written. This PR aims to speed up the function by * using a per-length input string length replacement map * binary searching the replacement map instead of a linear search Diffent, but functionally equivalent implementations were compared: ```text * linear search in one big map: 348.44 µs * binary search in one big map: 334.46 µs * linear search in a per-length map: 178.84 µs * binary search in a per-length map: 154.54 µs * perfect hashing: 170.87 µs ``` The winner of this competition is "binary search in a per-length map". It does not introduce new dependencies, but has the slight disadvantage that it uses one instance of `unsafe` code. I deem this disadvantage acceptable, though. Nb. It was also tested if a variant that only stores the replaced string would be faster. This "optimization" proved to be slower for all implementations except "binary search in a per-length map", for which it has the same runtime. Without a clear advantage to use the "optimized version", I chose to use the more easy to read slice of tuples variant. Obviously, for all measurements: YMMV.