Consistent definitions and for attributes across signals

[coryan]

I have introduced some inconsistency in attribute names and values for the different signals (more or less intentionally, I wanted to see all the signals working, even if not "perfect"). Including:

• For most services spans, the rpc.method should be the name of the gRPC method, as in google.cloud.secretmanager.v1.SecretManager/CreateSecret
• For storage, the rpc.method should be the
• Errors should include the error.type field
• Traces and errors should not include rpc.service (rpc.method carries this)
• The rpc.system key should be replaced with rpc.system.name (same values)
• The gcp.resource.name key should be replaced with gcp.resource.destination.id (same values)
• The gcp.client.* keys should be present on metrics
• Include the the Schema URL is spans and metrics.
  - It should be set to "https://opentelemetry.io/schemas/1.39.0" on the instrumentation scope
  - Where this is not possible (because tracing_opentelemetry doesn't support it) we can omit it, or
  - Put it in an attribute gcp.schema.url

[westarle]

I updated this issue with some additional updates/gaps in traces, metrics.