Parquet: Add system config for unsafe Parquet ID fallback.

[rdblue]

This adds a SystemConfig setting to enable or disable unsafe Parquet ID fallback.

Unsafe Parquet ID fallback (ParquetSchemaUtil.pruneColumnsFallback) is Netflix-specific behavior that assigns column IDs by position if a file is missing IDs and there is no name mapping. This pre-dates the public release (a5eb3f6). This is only applicable for Netflix datasets that resolved columns by position in Parquet and could not use name mapping.

This PR is the first step to removing fallback ID assignment by adding an environment config that can enable it. We need to remove fallback ID assignment because it is not safe. For data from Spark or other systems with name-based evolution, fallback ID assignment will produce incorrect results when data file schemas have changed (dropped a column). Also, integrations have recently used this behavior accidentally by producing incorrect Parquet files with no field IDs. Removing this will help Iceberg producers to adhere to the spec.

Currently, fallback assignment behavior is triggered when a NameMapping is null and a file has no field IDs. This adds the ability to disable fallback assignment by passing an empty NameMapping that will result in the original file schema after mapping.

[rdblue]

@jackye1995, this is the fix I mentioned for Parquet data files.

[rdblue]

@jackye1995, @danielcweeks, @RussellSpitzer, could you look at this? I'd like to ideally get it into the next release since we have been allowing unsafe reads.

[aokolnychyi]

Optional: You could also check the system property when picking the default value in the constructor or add a method called nameMapping() to avoid two variables with similar names in build().

[rdblue]

I went to add this, but then I thought it was a bit confusing to have both the field and method. I think it should be okay to have an extra variable.

[aokolnychyi]

I am not sure including Netflix in the property name gives us any benefit. I'd consider just calling it any of these:

iceberg.unsafe-parquet-id-fallback.enabled
iceberg.parquet.unsafe-id-fallback.enabled

Up to you, though.

[rdblue]

I like having Netflix in the name because it signals that people should not use this. It is not a feature, it is an artifact of Iceberg's history.

[aokolnychyi]

I am +1 on adding a conf now and disabling it in 2.0. I think the fallback can lead to silent data correctness issues and that's not good.

Is there an easy way to test this?

[Fokko]

LGTM. I've added the 1.5 milestone as well to make sure that we can remove this in 2.0

[rdblue]

Merged. Thanks for reviewing, @aokolnychyi and @Fokko!