Better project tooling for snippets

[jack-berg]

Up till now, we use kitchen-sink.yaml as a blunt instrument to:

• Demonstrate the full configuration surface area of the schema
• Validate that the schema works as we expect (i.e. make validate-examples)

This is results in a variety of problems:

• kitchen-sink.yaml is huge!
• Despite our best effort, kitchen-sink.yaml can't express all the configurable surface area. For example, see Add schema for composite sampler #390 using bits of the parent based sampler configuration, which has 5 configurable sampler properties, to express a new sampler.
• kitchen-sink.yaml configuration is often nonsensical, as a result of the effort to document all the surface area.
• kitchen-sink.yaml is annotated with comments generated from the JSON schema and meta schema, which is good for consistency, but limits our ability to convey bits of information about a specific example to users.

I think what we really need is:

• A directory of snippets, e.g. /snippets
• Where each file in /snippets contains a narrow demonstration of a particular piece of the larger schema
• With build tooling which validates that each file adheres to the particular type it is demonstrating, leveraging a file naming convention of the form {type}_{snippet_description}.yaml with build tooling validating according to the {type} extracted from the file name.
• Where snippets do not contain generated comments from the JSON schema and meta schema, but instead only include ad-hoc comments where needed
• The generated schema-docs.md could leverage these snippets to detect usages of each type, and either link over to those snippets or directly embed their contents in the markdown.
• And where this tooling ultimately allows kitchen-sink.yaml to be deleted, as it is essentially decomposed into a bunch of smaller focussed pieces.

[marcalff]

Up till now, we use kitchen-sink.yaml as a blunt instrument to:

* Demonstrate the full configuration surface area of the schema

* Validate that the schema works as we expect (i.e. `make validate-examples`)

This is also a torture test for SIG implementations:

https://github.com/open-telemetry/opentelemetry-cpp/blob/main/functional/configuration/shelltests/kitchen-sink.test

[jack-berg]

This is also a torture test for SIG implementations:

Oh yes. We do that in java in a couple of places as well. SIG implementations could leverage snippets to do similar things in principle. Though, there's something nice / tortuous about exercising so much of the schema all at once like kitchen-sink.yaml tests do.