os: add deadline methods for File type

os: add deadline methods for File type

Add SetDeadline, SetReadDeadline, and SetWriteDeadline methods to os.File,
just as they exist today for the net package.

Fixes #22114

Change-Id: I4d390d739169b991175baba676010897dc8568fa
Reviewed-on: https://go-review.googlesource.com/71770
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>