tsaucer/run TPC-H examples in CI

[timsaucer]

Which issue does this PR close?

Closes #696
Closes #712

Rationale for this change

This PR sets up a work flow to generate TPH-C 1Gb data set in CI, runs the 22 examples, and compares their results to the
known answer file. By adding this PR we improve the robustness of our test suite.

What changes are included in this PR?

This PR adds the following changes:

• Adds CI workflow to generate TPH-C data set and answer file. The results are cached from run to run.
• Adds pytest file to run all 22 examples and compare them to the answer file
• Exposes substring operation that was missing. Sometime between 36.0.0 and 38.0.0 substr was performing the operation instead.

Are there any user-facing changes?

substring function exposed in python.

Additional context

This PR replaces #710 which contains a lot of intermediate testing steps. This MR should be cleaner to review.

[timsaucer]

@Michael-J-Ward It looks like we have a potential regression between 37.1.0 and 38.0.0. Namely substr on 37.1.0 would accept a start and length, the parameters that should apply to substring. I was using substr incorrectly but it worked by accident on 37.1.0 because substr and substring were calling the same underlying function. In 38.0.0 this is updated and substr now fails if you pass it two parameters.

This PR includes exposing substring which was missing on the python side.

[andygrove]

Awesome. Thank you @timsaucer