go/types: rename (historic) flag "-list" used for go/types testing

go/types: rename (historic) flag "-list" used for go/types testing

Rename -list flag to -errlist to avoid confusion with the go
test flag -list (introduced later).

This flag is only needed to get an error list when running the
go/types test harness manually on select files, e.g., as in:

	go test -run=Check -files=x.go -errlist

Change-Id: I67febcf968d2d8f4ff00c81eea7b2df723560eac
Reviewed-on: https://go-review.googlesource.com/84378
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>