Remove deprecated "time" crate

[kolen]

Removed time crate, which is deprecated, replaced time::precise_time_ns with standard library's std::time::Instant.

I'm not sure if it worsened "smoothness" of emulation. It feels the same after this change. I'm not sure that std::time::Instant is as precise as time::precise_time_ns on most systems. However, it all boils down to thread::sleep, which can't be very precise, I think, due to nature of schedulers in standard non-realtime OSes, so nanosecond-grade precision for time measurements is probably not as important.

To get feeling how std::time::Instant works, I ran the following script:

use std::time::Instant;

fn main() {
    let mut t = Instant::now();
    loop {
        println!("{:?}", t.elapsed());
        t = Instant::now();
    }
}

It outputs something like this:

73ns
41ns
41ns
75ns
42ns
42ns
76ns
43ns
41ns
74ns
44ns
44ns
75ns
41ns
42ns
77ns
41ns
41ns

So probably quite precise on my system (Mac OS). Not tested on Linux and Windows.

[kolen]

Relevant issue: rust-lang/rust#32626

On Linux, both functions seems to use the same syscall: time, std

[kolen]

I compared implementations of precise_time_ns and Instant::now, and for unices, Mac OS and Windows they use the same system calls, so with high certainty time crate can be replaced with Instant from standard library.

[pacmancoder]

Thanks! I'll merge that.