go/types, types2: remove need for invalidAST prefix in error calls

go/types, types2: remove need for invalidAST prefix in error calls

Since we already provide the error code, the prefix can be deduced
automatically.

Except for the changes in errors.go, the updates were made with
regex find-and-replaces:

check\.error\((.+), InvalidSyntaxTree, invalidAST\+    =>
check.error($1, InvalidSyntaxTree,

check\.errorf\((.+), InvalidSyntaxTree, invalidAST\+    =>
check.errorf($1, InvalidSyntaxTree,

Change-Id: Ia02fc56ac7a8524bdf0c404ff2696435408327e9
Reviewed-on: https://go-review.googlesource.com/c/go/+/441975
Run-TryBot: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>