revert: restore row_columnar.rs benchmark and remove jvm_shuffle.rs

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: andygrove

native/core/Cargo.toml

@@ -122,7 +122,7 @@ name = "bit_util"
 harness = false
 
 [[bench]]
-name = "jvm_shuffle"
+name = "row_columnar"
 harness = false
 
 [[bench]]