希望 Update<T>().SetSource(data) 可以简写为 Update<T>(data)

代码举例如下
``` java
//现在的方式
freeSql.Update().SetSource(data).UpdateColumns(o => o.Name).ExecuteAffrows();

//希望的方式。希望可以兼容省掉 .SetSource(data) 看起来更简短也更加容易理解
freeSql.Update(data).UpdateColumns(o=>o.Name).ExecuteAffrows();
```

Start at the Update() and SetSource(data) entry points to understand how update sources are currently represented and whether an overload can preserve existing behavior. Done means Update(data) supports the shown UpdateColumns(...).ExecuteAffrows() flow while retaining compatibility with the existing SetSource form.

Written by the indexing model from the issue text.