Added separate CI and CD workflows

[tdulcet]

This backports many of the same improvements that I made to PRPLL-NTT in gwoltman/gpuowl#7 and gwoltman/gpuowl#8.

• Changed the existing CI workflow into a separate CD workflow
  • Changed to build the Linux executable on CentOS 7 instead of Ubuntu 24.04
    • This lowered the required glibc version from 2.39 to 2.17.
  • Changed to build the macOS executables on macOS 26 instead of 14/15 (still targeting macOS 11)
  • (This kept the separate MSVC and MSYS2 executables on Windows, but you should probably pick just one. The CI would still test both.)
• Added new CI workflow
  • Added tests with multiple Ubuntu and macOS versions
  • Added tests with Clang on Linux and Windows
  • Changed to build the debug executables, as the CD workflow now builds the release executables
• Updated Makefile
  • Added new DEBUG flag
  • Added separate C and C++ arguments
  • Removed separate optimization flags based on the compiler, including obsolete flags for GCC
• Updated MSVC project file
  • Enabled compiler warnings
  • Removed obsolete and redundant optimization flags
• Enabled GCC/Clang to check the printf style arguments to the logprintf() function calls

Also see: primesearch/mfaktc#111