Win32: Misc. performance improvements

[Cacodemon345]

Summary

Call timeBeginPeriod only once on startup. This should avoid CPU overhead when timing CPU frames.

Use SetProcessInformation to make the OS better handle our threads on big/small cores (i.e. Intel Alder Lake or later).

Checklist

• I have tested my changes locally and validated that the functionality works as intended
• I have discussed this with core contributors already
• This pull request requires changes to the ROM set
  • I have opened a roms pull request - https://github.com/86Box/roms/pull/changeme/

References

None.