Peternator7/update phf logic

[Peternator7]

After some benchmarking, allocating a string appears to be slower than doing the if-else chain until a pretty large number of variants is hit. With that in mind, updating the PHF logic to be slightly different in the case insensitive scenario.

• store the natural case, lower case and upper case in the map.
• check the map and always fallback to if-else if it isn't present.