go/types: reorganize error codes into categories

In CL 264179, some reorganization of error codes was deferred in order
to minimize diffs between patch-sets.

This CL reorganizes the error codes as discussed. It is a pure
reordering, with no material changes other than the changing of internal
const values.

For #42290

Change-Id: I0e9b421a92e96b19e53039652f8de898c5255290
Reviewed-on: https://go-review.googlesource.com/c/go/+/266637


Run-TryBot: Robert Findley <rfindley@google.com>
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Trust: Robert Griesemer <gri@golang.org>
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Reviewed-by: Robert Griesemer <gri@golang.org>