CloudWatch: move QueryData input parsing types to separate package (#57165)

* CloudWatch: move parse request types separate package

* Move metric query constants, unexport metricDataQuery json decoding type

* Unexport isSearchExpression

pkg/tsdb/cloudwatch/models/query_error.go

@@ -0,0 +1,12 @@
+package models
+
+import "fmt"
+
+type QueryError struct {
+	Err   error
+	RefID string
+}
+
+func (e *QueryError) Error() string {
+	return fmt.Sprintf("error parsing query %q, %s", e.RefID, e.Err)
+}