Investigate massive memory leak

[spaghettidba]

When running for 15 minutes or more, it ends up using a lot of memory. Looks like Strings are the most allocated objects (sql statements).

[spaghettidba]

Reduced memory usage by discarding already saved normalized queries and keeping only the Int64 hash. See commit 547463a

Might not be enough for the cases where the queries are extremely volatile. One factor that might be driving the volatility is TVPs, where the number of values captured in the incoming workload is extremely varying and leads to masive INSERT...VALUES statements of different sizes, when it should be recording only the call to the TVP instead.

[spaghettidba]

The memory leak was due to events queuing up in the listener, so I implemented a cache on disk to reduce memory consumption