Add performance tests to measure heap memory

[tomuben]

Background

We got customer feedback about increased memory consumption of the script-language-container, between different versions.
In order to check if the UDF client or some dependency increase the memory consumption we should add new performance tests which measure the heap and compare between different version (the pre-installed slc of the DB and a new candidate).

We see two options:

• Write an UDF which uses the language specific API to gather memory consumption:
  • Java: Use NMT and Runtime.totalMemory()
  • Python: Use resource
• Write an UDF which spawns a new process which tracks the memory consumption, writes to a temporary file, which is then read and emitted by the UDF
• Also it would be good to have two kinds of UDF's: One which are as slim as possible (to measure the memory usage of the VM/runtime) and one which does some memory expansive stuff.

Acceptance Criteria

Write Python and Java Performance tests with the above requirements.