Replaces draft #5873.

@open-telemetry/java-instrumentation-maintainers in the 9/21 Java SIG meeting I brought up bringing the file configuration prototype into the java agent, and received feedback that it will be important to specify other java agent properties besides the SDK in a configuration. Examples include accessing jmx configuration, and other standard properties like otel.javaagent.debug=true.

This PR extends file configuration tooling to include access to configuration not part of the configuration schema. Summary:

• A user specifies both SDK and java agent configuration in a single YAML file, and sets OTEL_CONFIG_FILE to the file path
• Autoconfigure detects that OTEL_CONFIG_FILE is set and that opentelemetry-sdk-extension-incubator is on the classpath, and:
  • Parses / interprets the config file to configure the SDK
  • Converts the OpenTelemetryConfiguration model to a generic ExtendedConfigProperties representation accessible via AutoConfiguredOpenTelemetrySdk#getConfig()
• ExtendedConfigProperties implements ConfigProperties and adds some additional methods for accessing nested complex configuration types (nested maps, and lists of maps)
• The opentelemetry java agent accesses ExtendedConfigProperties and uses it for configuration

Suppose you have a configuration file with contents like:

file_format: "0.1"
tracer_provder:
  processors:
    - batch:
        exporters:
          otlp:
javaagent:
  debug: true
  jmx:
    foo: bar

In java, you use the file to configure the SDK, as well as access the extended "javaagent" portion of the schema as follows:

export OTEL_CONFIG_FILE=/path-to-config.yaml
...
AutoConfiguredOpenTelemetrySdk autoConfiguredSdk = AutoConfiguredOpenTelemetry.builder().build();
ExtendedConfigProperties configProps = (ExtendedConfigProperties) autoConfiguredSdk.getConfig();

ExtendedConfigProperties javaagentProps = configProps.getConfigProperties("javaagent");
Boolean debug = javaagentProps.getBoolean("debug");
ExtendedConfigProperties jmxProps = javaagentProps.getConfigProperties("jmx");
String foo = jmxProps.getString("foo");

assert foo.equals("bar");

// Or use dot notation 
assert configProps.get("javaagent.jmx.foo").equals("bar");
assert configProps.get("javaagent.debug").equals(true);