Release manager should review lucene benchmarks before building release candidates

### Description

We were about to release Lucene 9.4.0 with an important performance regression. This regression was showing up in the benchmarks but obviously we missed reviewing them. The regression was actually caught during the daily monitoring of Elasticsearch development instead.

Speaking to other Lucene committers we thought that it may be a good idea to add a new task to the release manager handbook to review the Lucene benchmarks before building the release candidates. Obviously we are not expecting the release manager to find all regressions but something as obvious as the one in Lucene 9.4.0 would have been possible.

wdyt?

Locate the release manager handbook referenced in the issue and read its release-candidate preparation steps. Add a task to review Lucene benchmarks before building release candidates, with completion shown by the handbook explicitly including that review.

Written by the indexing model from the issue text.