time: implement Compare method

time: implement Compare method

Fixes #50770.

Change-Id: If0104883bb409ec85827fa5b570f68099ad4fd1d
Reviewed-on: https://go-review.googlesource.com/c/go/+/382734
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: hopehook <hopehook@golangcn.org>
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Reviewed-by: Joseph Tsai <joetsai@digital-static.net>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>