[sdk-metrics] [sdk-trace] ensure resource is not auto-merged with default when it is provided to constructor

[Marc Pichler]

Description

Currently we always merge Resource.default() with the constructor-provided resource. However, the spec states that this should only happen when no resource is provided:

The SDK MUST provide access to a Resource with at least the attributes listed at
Semantic Attributes with SDK-provided Default Value.
This resource MUST be associated with a TracerProvider or MeterProvider
if another resource was not explicitly specified.

A later section states that:

Note: This means that it is possible to create and associate a resource that
does not have all or any of the SDK-provided attributes present.

The goal of this issue is to change the resource handling trace and metrics SDKs to be spec-compliant.

This issue is considered done when:

• Resource.default() is not auto-merged with the constructor-provided resource in sdk-metrics
• Resource.default() is not auto-merged with the constructor-provided resource in sdk-trace-base
• Resource.default() is not auto-merged with the constructor-provided resource in sdk-trace-node
• Resource.default() is not auto-merged with the constructor-provided resource in sdk-trace-web
• TBD: if any other SDK packages are stable by the time we work on this, also align them with the specification.

NOTE: if this is not applicable for one of the packages listed above when this issue is being implemented, state why this is the case in a comment, and link that comment below the list item before ticking the checkbox. Otherwise link the PR.

Additional resources:

Links to non-spec-compliant sections:

• opentelemetry-js/packages/opentelemetry-sdk-trace-base/src/BasicTracerProvider.ts

  Line 83 in 47444f2

   this.resource = Resource.default().merge(this.resource); 

• opentelemetry-js/packages/sdk-metrics/src/MeterProvider.ts

  Lines 49 to 51 in 0f6518d

   const resource = Resource.default().merge( 
     options?.resource ?? Resource.empty() 
   );