Fix unsafe bool usage

[mborland]

Replace unsafe bool usage in type promotion with boost::math::tools::promote_args_t. Additionally, refactor sonarlint warnings.

[jzmaddock]

Question: do we want to remove the inline and noexcept qualifiers? Is a likely use case that this may be used in code which is maybe or maybe not constexpr? If not then maybe we should perhaps devise a static_assert that will fail when instantiated in a non-constexpr context, and/or make the qualifiers consteval in C++20 and later?

[mborland]

The inline qualifier was removed because it is redundant. The noexcept qualifier was removed because at compile time the function is noexcept, but at runtime the STL does not require it. This matches the now accepted C++23 proposal for making some of cmath constexpr.