Coding - Introduce compile-time sqrt constants and use them consistently (#789)

Coding - Introduce compile-time sqrt constants and use them consistently (#789)

- Add M_SQRT2 macro in multiple sources and replace runtime sqrt/Sqrt(2) calls with the macro
- Add SQRT_3 constexpr in IGESGraph_Color and Bnd_OBB and replace Sqrt(3) usages
- Make BSplSLib_zero a constexpr array
- Replace a few computed sqrt literals with compile-time constants for clarity and consistency