NES: fixed windows slow emulation (was due to windows Sleep function)

`std :: thread :: sleep` is not the same in all platforms.
Rust uses `libc::nanosleep` in Linux which can take a number of nano seconds,
sleeping may not be exactly the time it was requested but at least
close.

On the other hand, Rust uses windows api function `Sleep`, it takes a
number of **Milliseconds**, this is not very good for small sleeps,
but this is what I want, and what the emulator was doing the whole time.

Changed the number of clocks to a whole frame, now that the APU is not
very affected by the sleeping time like before, this is not much of a
problem and now the emulator can run smoothly in windows. :)

*they should fix their Kernal*.

nes_ui_base/src/nes.rs

@@ -229,7 +229,7 @@ impl<P: UiProvider + Send + 'static> NES<P> {
 
         let mut last = std::time::Instant::now();
         const CPU_FREQ: f64 = 1.789773 * 1E6;
-        const N: usize = 2000; // number of CPU cycles per loop, lower is smoother
+        const N: usize = 29780; // number of CPU cycles per loop, one full frame
         const CPU_PER_CYCLE_NANOS: f64 = 1E9 / CPU_FREQ;
 
         let mut average_apu_freq = CPU_FREQ / 2.;