Removes shadowing from the benchmarks. It isn't *strictly* needed. We do
have to rework the documentation on how to run the benchmark, but it
still seems to work if you run everything through gradle.
* Allow to run client benchmark as an uberjar
* Busy wait to avoid accidental skew on low target throughput rates
* Trigger and wait for full GC to happen between trials
* Add missing SuppressForbidden to allow System.gc in client benchmark