chore: Fix merge conflicts from merging comet-parquet-exec into main (#1323)

* Remove extra files after merging main into comet-parquet-exec.

* Clean up imports in CometTestBase.

Author: mbutrovich

native/spark-expr/src/lib.rs

@@ -22,9 +22,7 @@
 mod error;
 
 mod kernels;
-mod schema_adapter;
 mod static_invoke;
-pub use schema_adapter::SparkSchemaAdapterFactory;
 pub use static_invoke::*;
 
 mod struct_funcs;