Implement inheritance through `spec_dict` merging in compilation

[moshewe]

Implemented in Workflow. I wasn't able to run the tests in the library (no explanation I could find on how to do that), but I've run the code with my own app and it works.

I've tested it with a hierarchy of 3 classes, A->B->C, and various inheritance scenarios. E.g., entrypoint was defined in A, and I can now see it in the compilation result of C.

Addresses #19 , but also some others I saw.

[CLAassistant]

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