2 - Create language-specific SBOM-generator for Go

Proposal

Once 1 - Add sbom command to gemnasium analyzers (#364622 - closed) has been completed, we'll have a new sbom command available to the gemnasium, gemnasium-maven and gemnasium-python analyzers. In order to provide more fine-grained control over the sbom generation process, we want to start splitting the three gemnasium analyers into smaller tools that handle only a specific language.

The purpose of this issue is to create a language-specific SBOM-generator for Go. We'll eventually support other languages, but by focusing on only a single, it will give us an opportunity to determine a pattern for implementing multiple language generators, as well as how to structure the project layout, shared code and tests.

This SBOM generator will be a proof-of-concept, and doesn't need to be made generic, we just need to come up with the simplest approach that will work for a specific analyzer.