MSSQL: Issue with CTE anchors

Hi, the following is a valid MSSQL syntax

When parsed with the `sql-parser-rs`

```sql
WITH RecursiveCTE AS (
-- Anchor member
SELECT TOP 1
[ID],
CAST([Amount] AS NUMERIC) AS [Amount],
CAST([Balance] AS NUMERIC) AS [Balance],
(SELECT TOP 1 [FixedValue] FROM [Settings] ORDER BY [ID] DESC) AS [Constant]
FROM [Transactions]
ORDER BY [ID] ASC

UNION ALL

-- Recursive member
SELECT
[ID] + 1 AS [ID],
CAST([Amount] * 0.8 AS NUMERIC) AS [Amount],
CAST(([Amount] * 0.8 - [Constant]) AS NUMERIC) AS [Balance],
[Constant]
FROM RecursiveCTE
WHERE [Balance] > 0
)
SELECT [ID], [Balance]
FROM RecursiveCTE
ORDER BY [ID] ASC;
```

it gives the following error

```bash
sql parser error: Expected: ), found: UNION at Line: 11, Column: 5
```

https://learn.microsoft.com/en-us/sql/t-sql/queries/with-common-table-expression-transact-sql

Comienza reproduciendo la consulta CTE de MSSQL proporcionada en sql-parser-rs y compara el manejo de CTE del parser con la documentación de Microsoft enlazada. Rastrea el punto de entrada del parser que informa de unexpected UNION y, a continuación, añade una prueba de regresión que demuestre que la consulta se analiza correctamente.

Escrito por el modelo de indexación a partir del texto del issue.