Add CI check that tool is deterministic

[siddharth-krishna]

Ah, this is because iterating through a set results in a non-deterministic order (see also #50 and #67). This makes it very difficult to debug regressions, because I rely on the --verbose flag and a diff tool to find out which transformation caused the regression. But with nondeterministic behaviour, there are too many changes in the diff..

I'm considering adding a check to CI that runs the tool on a small benchmark ~5-10 times and ensures that all intermediate tables are identical across runs.

Originally posted by @siddharth-krishna in #166 (comment)