go/types: match types2 errors for incorrect method receiver count

go/types: match types2 errors for incorrect method receiver count

Use "method has no receiver" and "method has multiple receivers"
in error messages for invalid receiver counts, matching the
corresponding types2 errors.

For #54511.

Change-Id: I96fc99440d6206c74e9416069db052234baa8248
Reviewed-on: https://go-review.googlesource.com/c/go/+/424934
Reviewed-by: Alan Donovan <adonovan@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>