fix: Fallback to Spark if scan has meta columns

[viirya]

Which issue does this PR close?

Closes #.

Rationale for this change

Currently Comet scan cannot work with Iceberg reader internally if there is meta columns. We should fallback to Spark for the case before we can support meta column.

What changes are included in this PR?

How are these changes tested?

Manually test with Iceberg tests.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 57.14286% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 34.31%. Comparing base (c3023c5) to head (1a07658).
⚠️ Report is 752 commits behind head on main.

Files with missing lines	Patch %	Lines
...org/apache/comet/CometSparkSessionExtensions.scala	57.14%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #997      +/-   ##
============================================
+ Coverage     34.03%   34.31%   +0.27%     
- Complexity      875      889      +14     
============================================
  Files           112      112              
  Lines         43289    43438     +149     
  Branches       9572     9617      +45     
============================================
+ Hits          14734    14904     +170     
+ Misses        25521    25509      -12     
+ Partials       3034     3025       -9     

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