Related to #8402.

This PR solves lingering problems with the declarative config generated pojos. With it, all the issues I know of related to the generated POJOs are resolved, unblocking stabilization of declarative config.

1. Experimental properties have public getter / setter API surface area on stable types. This is a blocker for stabilizing.
2. When a property is stabilized and a user continues to use the old */development version, is will be silently dropped from the parsed model.

How it solves these issues:

• Every type with experimental properties now has a <Type>ModelAccessor class in io.opentelemetry.sdk.autoconfigure.declarativeconfig.model.internal. This contains generated, type safe accessors for setting / getting experimental types from the stable parent type.
• Every getter now returns the */development version of its property if available and the stable version is not set.
• Every type now has a @JsonAnySetter method withExtensionProperty(String name, @Nullable Object value) for handling JSON schema additionalProperties: true and experimental properties:
  • If name is equal to a known stable property after stripping /development suffix, log a warning to prefer the stable variant, convert value to the stable property type and save it.
  • If name corresponds to known experimental property, convert value to the experimental property type and save it.
  • If the type supports additionalProperties, save it.
  • Else, log a warning.