UPDATE: Adds 56 functions in the Statistical section

Uses statrs for numerical functions

REFACTOR: Put statistical functions on its own module

This might seem counter-intuitive but the wasm build after this refactor
is 1528 bytes smaller :)

base/src/functions/statistical/mod.rs

@@ -0,0 +1,23 @@
+mod beta;
+mod binom;
+mod chisq;
+mod count_and_average;
+mod covariance;
+mod devsq;
+mod exponential;
+mod fisher;
+mod gamma;
+mod geomean;
+mod hypegeom;
+mod if_ifs;
+mod log_normal;
+mod normal;
+mod pearson;
+mod phi;
+mod poisson;
+mod standard_dev;
+mod standardize;
+mod t_dist;
+mod variance;
+mod weibull;
+mod z_test;