Investigate integrating with fast_float

[madolson]

I've seen a couple of posts recently about how both dragonflyDB and Redis integrated with https://github.com/fastfloat/fast_float to improve parsing of doubles. We use strtod (exposed as getDoubleFromObject) in sorted set computation. The library was implemented in C++, but we should be able to extract out the needed code that solves our specific use case.