QuotedPrefix is similar to Unquote, but returns the quoted string verbatim
and ignores any data after the quoted string.
Fixes #45033
Change-Id: I9f69fe9e3e45cbe9e63581cf1b457facb625045d
Reviewed-on: https://go-review.googlesource.com/c/go/+/314775
Trust: Joe Tsai <joetsai@digital-static.net> Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>