The way `@fptw` was handled has been wrong for a long time but I finally figured out. This updates all the backends to do the right thing.
Other more minor changes:
- The code that reads the CPU state has been updated to be compatible with [snapshot](https://github.com/0vercl0k/snapshot). It also should be now able to load precise values for 80-bit registers. Loading 'old' dumps should also work as they were before (with the buggy code) to not break them
- Updated bxcpu to be able to load `@fpst` registers with a `frac` / `exponent` (cf https://github.com/yrp604/bochscpu/commit/cab805101cbcaf0c722ef266abdece8745676f44)
- Minor updates to the README
- Update the CI to get rid of warnings as well as removing the CodeQL scanning (it hasn't reported a single hit since it's been turned on -_-)