Why non-atomic delete and upsert?

### Question

The implementation of the `delete` and `upsert` operation make an deliberate choice to create multiple snapshots, breaking the atomicity expectation.

For example, if I start a `delete` operation to remove some entries, I do not expect consumers of the data to see a snapshot with some but not all of the entries gone.

Given that the implementation choice looks very deliberate, I'm curious about the rationale for it?

It seems that other clients of the library expect atomic operation as well, for example https://github.com/apache/iceberg-python/issues/3076

该 issue 未指定文件、测试或入口点；首先定位 PyIceberg 中 delete 和 upsert 的实现，并查看它们如何创建快照。确定观察到的多个快照行为是否是有意设计的，然后在进行更改之前记录其依据或定义所需的原子行为。

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