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/test/statistical/test_fn_poisson.rs

@@ -0,0 +1,41 @@
+#![allow(clippy::unwrap_used)]
+
+use crate::test::util::new_empty_model;
+
+#[test]
+fn test_fn_poisson_dist_smoke() {
+    let mut model = new_empty_model();
+
+    // λ = 2, x = 3
+    // P(X = 3)  ≈ 0.180447045
+    // P(X <= 3) ≈ 0.857123461
+    model._set("A1", "=POISSON.DIST(3, 2, FALSE)");
+    model._set("A2", "=POISSON.DIST(3, 2, TRUE)");
+
+    // Wrong arg count
+    model._set("A3", "=POISSON.DIST(3, 2)");
+    model._set("A4", "=POISSON.DIST(3, 2, TRUE, FALSE)");
+
+    // Domain errors
+    model._set("A5", "=POISSON.DIST(-1, 2, TRUE)"); // x < 0
+    model._set("A6", "=POISSON.DIST(3, -2, TRUE)"); // mean < 0
+
+    // λ = 0 special cases
+    model._set("A7", "=POISSON.DIST(0, 0, FALSE)"); // 1
+    model._set("A8", "=POISSON.DIST(1, 0, FALSE)"); // 0
+    model._set("A9", "=POISSON.DIST(5, 0, TRUE)"); // 1
+
+    model.evaluate();
+
+    assert_eq!(model._get_text("A1"), *"0.180447044");
+    assert_eq!(model._get_text("A2"), *"0.85712346");
+
+    assert_eq!(model._get_text("A3"), *"#ERROR!");
+    assert_eq!(model._get_text("A4"), *"#ERROR!");
+    assert_eq!(model._get_text("A5"), *"#NUM!");
+    assert_eq!(model._get_text("A6"), *"#NUM!");
+
+    assert_eq!(model._get_text("A7"), *"1");
+    assert_eq!(model._get_text("A8"), *"0");
+    assert_eq!(model._get_text("A9"), *"1");
+}