feat(bench/deno_common): track Date.now() as upper bound

[AaronO]

This is another simple extension of the cli/bench/deno_common.js "benchsuite".

It benches Date.now() (a v8 builtin) to provide an indication of the upper bound for non-NOP ops.
(This should be our practical upper bound for all ops, even with v8 Fast API)

Benches as of 1.8.2

On my M1 Air:

❯ deno -V; deno run --unstable -A ./cli/bench/deno_common.js
deno 1.8.2
date_now:            	n = 500000, dt = 0.021s, r = 23809524/s, t = 42ns/op
perf_now:            	n = 500000, dt = 0.700s, r = 714286/s, t = 1400ns/op
url_parse:           	n = 50000, dt = 0.712s, r = 70225/s, t = 14240ns/op
read_zero:           	n = 500000, dt = 0.758s, r = 659631/s, t = 1516ns/op
write_null:          	n = 500000, dt = 0.739s, r = 676590/s, t = 1478ns/op