[Release] Add performance comparison between Release Candidate and previous release

### Describe the enhancement requested

On the 12.0.0 release we introduced a performance regression and we had to create the 12.0.1 release to fix it.
The performance regression could have been found during release candidate verification if we would have had some performance comparison between the new Release Candidate and the old Release.
There has been some discussion on the Arrow biweekly community call to introduce a step during the release to generate a conbench comparison between the new RC and the previous release.

This issue is to track this improvement and add this step so we have more data around performance when voting for the release.

### Component(s)

Release