Unable to derive from ResourceDetector and create a Resource

[dbarker]

Describe your environment

main branch at 57114c5

Steps to reproduce
Derive a custom resource detector from ResourceDetector and try to call the constructor of Resource.

What is the expected behavior?
Compiles and creates a resource with the provided attributes

What is the actual behavior?
Fails to compile

Additional context

• Resource adds the OTELResourceDetector as a friend here but not ResourceDetector.
• ResourceDetector doesn't provide a protected method to create a resource with just the attributes detected.