Revisit directory structure and package scoping

[grayside]

Package naming and scope seems like it's been slightly outgrown by the way the code has been implemented. As a result, it's difficult to know where to look to see code for the different aspects of the tool.

A few examples of this are gathered here:

• Testing is a main feature of this tool, but the testing code is implemented inside util package.
• util/config.go seems to be for OpenAPI file parsing. A more specific name would be helpful.
• Were I to guess what the lifecycle package is about, I'd expect to find organization of all build, deploy, test, and teardown steps. However, it's only build.
• The gcloud package is in fact a subset of Cloud Run specific operations, the use of gcloud is an implementation detail.
• Because of the lack of clarity in some of the other package names, I find it difficult to recall what might be found in sample.

Happy to discuss possible code organization improvements.

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This issue affects two categories in my review of the repository:

• Adoption: Can this project be found and does it provide enough context on when and how to use it? Does it inspire confidence as a well-maintained project?
• Internals: Is the implementation efficient, effective, and maintainable?