improve `cosc(::Float32)` and `cosc(::Float64)` accuracy (#59087)
Accomplished by:
* Using minimax instead of Taylor polynomials. They're more efficient.
The minimax polynomials are found using Sollya.
* Using multiple polynomials for different subintervals of the domain.
Known as "domain splitting". Enables good accuracy for a wider region
around the origin than possible with only a single polynomial.
The polynomial degrees are kept as-is.
Fixes #59065
