fix: [iceberg] Fall back on dynamicpruning expressions for CometIcebergNativeScan

[mbutrovich]

Which issue does this PR close?

Closes #.

Rationale for this change

We're seeing issues on main with Iceberg tests due to CometIcebergNativeScan convert() failing to serialize a dynamicpruning expression, which leaves the CometBatchScan operator. When doExecuteColumnar() is called on that, we get the underlying Iceberg reader producing a type that Comet is not prepared for at the native columnar to row operator.

I think this is a new bug exposed by #3299.

What changes are included in this PR?

• Fall back on a dynamicpruning expression.
• Stricter exception throwing for failure scenarios at serialization time.

How are these changes tested?

New test, existing Iceberg tests should pass again.

[andygrove]

do we need this check more widely for all v2 scans?

[mbutrovich]

I'm not sure about the blast radius on that, it's possible/likely.

[andygrove]

Thanks @mbutrovich

[codecov-commenter]

Codecov Report

❌ Patch coverage is 50.00000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 59.96%. Comparing base (f09f8af) to head (0a3691f).
⚠️ Report is 906 commits behind head on main.

Files with missing lines	Patch %	Lines
.../comet/serde/operator/CometIcebergNativeScan.scala	25.00%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #3335      +/-   ##
============================================
+ Coverage     56.12%   59.96%   +3.83%     
- Complexity      976     1474     +498     
============================================
  Files           119      175      +56     
  Lines         11743    16165    +4422     
  Branches       2251     2681     +430     
============================================
+ Hits           6591     9693    +3102     
- Misses         4012     5124    +1112     
- Partials       1140     1348     +208     

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