Syx snapshot improve

[enisrat]

• SYX in cputlb.c fixes and streamlining
  • The semantics of SYX snapshot and QEMU`s notdirty tracking are basically equal
  • Leverage existing notdirty_write for fast snapshot
• Clear TB cache selectively when restoring snapshot to improve performance
• Change logic in syx_snapshot_new as to how i understand before_fuzz_cache. As we have a static syx_snapshot_state, no need to free. I tested and was able to successfully cache bdrv writes before the first snapshot, as intended

I submitted these changes months ago for QEMUv9. It worked for me for a while.
In here I stripped not related things and concentrate on syx snapshot.