internal/types: consistently use double quotes around ERROR patterns

internal/types: consistently use double quotes around ERROR patterns

Before matching the pattern, the double quotes are simply stripped
(no Go string unquoting) for now. This is a first step towards use
of proper Go strings as ERROR patterns.

The changes were obtained through a couple of global regexp
find/replace commands:

/\* ERROR ([^"]+) \*/   =>   /* ERROR "$1" */
// ERROR ([^"]+)$       =>   // ERROR "$1"

followed up by manual fixes where multiple "/* ERROR"-style
errors appeared on the same line (in that case, the first
regexp matches the first and last ERROR).

For #51006.

Change-Id: Ib92c2d5e339075aeec1ea74c339b5fecf953d1a0
Reviewed-on: https://go-review.googlesource.com/c/go/+/455718
Auto-Submit: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
Run-TryBot: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>