Integration Test Harness

[Ryanmtate]

Create integration test harness for packaged substream modules.

It should:

• Load substreams spkg module and use the grpc sf endpoint to test the consumption of the stream;
• Cache the results of the stream;
• Check runs against cached results;
• Save cached results to target folder (used by github actions);

[Ryanmtate]

See note in #63 on using substreams cli instead of the grpc client. There is a build script for setting up the substreams grpc client in the PR, but I have not been able to successfully get block response.