Reduce the frequency of `beforeTests` and `afterTests` in executors.

Previously, the behaviour was:
- call the `beforeTests` before the warmup
- call the `afterTests` after the warmup
- call the `beforeTests` before the benchmarks
- call the `afterTests` after the benchmarks

Now, the behaviour is:
- call the `beforeTests` before the warmup
- call the `afterTests` after the benchmarks

The `LocalExecutor` calls these methos more often to do classloading.