INSERT statements cannot be prepared with sql.DB.Prepare()

[ohaibbq]

We currently validate that the number of args passed matches the number of parameters for the query. When using prepared statements, arguments do not need to be passed until the query is executed.

Example:

	columnsWithEscape := []string{"`foo`", "`bar`"}
	placeholders := []string{"?", "?"}
	query := fmt.Sprintf(
		"INSERT `%s` (%s) VALUES (%s)",
		r.tablePath(projectID, datasetID, table.ID),
		strings.Join(columnsWithEscape, ","),
		strings.Join(placeholders, ","),
	)
	stmt, err := tx.Tx().PrepareContext(ctx, query)

Expected: a stmt is returned
Actual: err not enough query arguments is returned