Added support for distribution config in ConfigProvider

[robsunday]

Fixes #4770

This PR introduces Declarative Configuration support for distribution specific configuration.
The .distribution node is now available in the root of Declarative Configuration YAML file, as agreed on SIG.

Changes

ConfigProvider is extended with new operation to provide access to the .distribution node

For non-trivial changes, follow the change proposal process.

• Related issues #opentelemetry-configuration/issues/336
• Related OTEP(s) #
• Links to the prototypes (when adding or changing features)
• CHANGELOG.md file updated for non-trivial changes
• Spec compliance matrix updated if necessary

[carlosalberto]

cc @jack-berg

[trask]

the link points to the .instrumentation node

[jack-berg]

All instrumentation will have access to this. The original design of ConfigProvider intentionally limited the scope to the .instrumentation/development node, so as to avoid the questions about whether its appropriate / safe for instrumentation to have access to the SDK config model, including any secrets that may be present on the exporter nodes.

If we want to broaden scope, we need to have that conversation since its very reasonable that .distribution node will have the types of secrets that are in the SDK config model.

On a related note, why is this necessary?

The declarative config has separate parse and create methods that allow a distribution to access the .distribution node. For example in java:

OpenTelemetryConfigurationModel model = parse(new File(System.getEnv("OTEL_EXPERIMENTAL_CONFIG_FILE")));
DistributionModel distribution = model.getDistribution();
OpenTelemetrySdk sdk = create(model);

If there's not a strong need for this, the safe answer is to continue the status quo and not grant instrumentation access to more config than they need.

[jack-berg]

Requesting changes because I want to make sure we discuss this before merging.