Right now, we are heading toward singletons that are created per API to set / retrieve singletons.

For example, tracer has it's own tracer.tracer(), with that pattern.

Having the APIs loosely coupled with an explicit composition object requires the SDK / API consumer to be aware of all singletons, and set them themselves. If one is missed, one could end up with no emission of tracers / metrics and would require them to understand the whole OTel API and part of the code to debug.

We should consider a global object that has a method that requires configuration of all required APIs. This would ensure that the consumer has a quick reference that will ensure that the SDK will operate as desired.