Remove sampled exact aggregation tests
Remove sampled benchmarks
Fix intellij warning
Remove bootstrapped aggregation
Refactor aggregations

Introduce a new base class for aggregation functions that makes them
simpler to write.
Add missing presto-main dependency to presto-server

This was missed in the refactoring that moved the server code to presto-main.
As a result, the server fails to start when run via the launcher
Replace Unsafe with new Slice ByteArrays utility