primesieve-12.9

This is a new maintenance release, it is fully backwards compatible with the previous release.

• CMakeLists.txt: Speed up build by removing compile dependencies.
• Move private header files from /include to /src.
• src/CMakeLists.txt: Update for private header files in /src.
• test/CMakeLists.txt: Update for private header files in /src.
• Vector.hpp: Get rid of std::is_trivial which is deprecated in C++26.