Fix up ErrorMatcher from feedback

a) Rename the type and drop the constructor
b) Make MatchErrors() into a Test() method

For followup:

c) Consider making ByType() assumed
d) Consider making ByField() assumed and handle nil as "don't care"
e) Consider making ByValue() assumed and handle nil as "don't care"

Kubernetes-commit: 0a9f492eedf6dd68fee12e4606d3fef4d608d88f

pkg/registry/rest/validate_test.go

@@ -154,7 +154,8 @@ func TestValidateDeclaratively(t *testing.T) {
 			} else {
 				results = ValidateUpdateDeclaratively(ctx, tc.options, scheme, tc.object, tc.oldObject)
 			}
-			fieldtesting.MatchErrors(t, tc.expected, results, fieldtesting.Match().ByType().ByField().ByOrigin())
+			matcher := fieldtesting.ErrorMatcher{}.ByType().ByField().ByOrigin()
+			matcher.Test(t, tc.expected, results)
 		})
 	}
 }