systemtest oracle files are 65MB

[Dimitar Misev]

The oracle files in the systemtest are 65MB in total. This is almost half the size of the rasdaman repo.. and it'll likely get worse as we develop the systemtest with more tests.

Let's brainstorm a bit about some straightforward and simple way to improve this.

The most obvious idea: store checksums of the expected result outputs. Then when running the systemtest, checksums are computed of the outputs and compared to the expected ones. This also allows us to run tests with larger outputs (e.g. testing a query outputing a 1GB file).