Lack of benchmarks for RepartionExec

### Is your feature request related to a problem or challenge?

we need a way to measure improvements in #7001 that the tpch E2E benchmarks may not capture

### Describe the solution you'd like

add a new benchmark suite that targets repartionExec

### Describe alternatives you've considered

n/a

### Additional context

#7001

Start by reading the existing TPC-H E2E benchmarks and the context of #7001, then locate the RepartitionExec entry point in DataFusion. Add a benchmark suite that specifically exercises RepartitionExec and produces measurements that can reveal improvements not captured by TPC-H; done means the suite runs and reports comparable results.

Written by the indexing model from the issue text.