fix(cli): use Instant for test times

[mmastrac]

Fixes denoland/deno_std#4473

[iuioiua]

Nice

[iuioiua]

There are other instances of the use of SystemTime::now() in the codebase. How many of them should use Instant::now() instead, too? Documentation says it's good for measuring the duration between two points in time.

[mmastrac]

There are other instances of the use of SystemTime::now() in the codebase. How many of them should use Instant::now() instead, too? Documentation says it's good for measuring the duration between two points in time.

We should use SystemTime::now only in two cases:

• One, if we are using elapsed time since the UNIX_EPOCH (this is generally safe)
• Two, if we are printing a string date with the actual date/time

If we use SystemTime::now and a duration since anything but the unix epoch, that's definitely a problem!

[bartlomieju]

LGTM, from what I see the worst case is we're gonna get 0ms elapsed. Seems fine for tests.