Add Schema URL for resources

[pichlermarc]

Our resource implementation does not currently consider the (optional) concept of Schema URLs (as described in https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/resource/sdk.md#resource-creation).

To support this, we'll have to add it to the create and merge operations on the Resource, and we'll have to adapt the @opentelemetry/otlp-transformer package so that it populates the schema URL with the one from the SDK's resource

This issue is considered done when:

• [ ] Schema URL can be added using the Resource constructor
• [ ] Schema URL is handled according to the specification on Resource#merge
• [ ] A resource's Schema URL is exported via all OTLP exporters in this repository.

[github-actions[bot]]

This issue is stale because it has been open 60 days with no activity. Remove stale label or comment or this will be closed in 14 days.

[github-actions[bot]]

This issue is stale because it has been open 60 days with no activity. Remove stale label or comment or this will be closed in 14 days.