receipe generated functions should be in strictly snakecase

[Roger-luo]

currently @receipt simply convert a camel case type name into lowercase functions,

https://github.com/JuliaPlots/Makie.jl/blob/9a4821bcaf1cf0f09841e659dd2a6eb81afe6527/MakieCore/src/recipes.jl#L3

this can be very hard to read when the name is long, e.g BitStringHistgram will be convert to bistringhistgram instead of bitstring_histgram. I think it is very hard to follow Julia's style guide on function naming when doing this automatically, so maybe @receipt should just convert all camel case type name to snake case function, which is much clearer on the mapping rules and much easier to read.