High precision atan etc, pow optimization for big values

[Safari77]

same as #374 but rebased to main and has pow optimization (precision 200 digits) and also Dynamic precision for {sin,cos,atan}_series, inv trigs accurate up to 10e369. Let me know if you want to keep pow like it is now.

Configurable values for the algorithm change can be modified here:
bigrat.rs

// Use exp/ln approximation if:
// 1. The denominator is large (e.g. ^0.0001), indicating a complex decimal root.
// 2. The numerator is large AND it's a root (e.g. ^210.1 = ^2101/10).
let large_root = rhs.den > BigUint::from(1000u64);
let large_power = rhs.den > BigUint::from(1u64) && rhs.num > BigUint::from(100u64);