Add CoaleseBatches benchmark

Author: alamb

arrow/Cargo.toml

@@ -161,6 +161,12 @@ name = "filter_kernels"
 harness = false
 required-features = ["test_utils"]
 
+[[bench]]
+name = "coalesce_kernels"
+harness = false
+required-features = ["test_utils"]
+
+
 [[bench]]
 name = "take_kernels"
 harness = false