Accept faas.name and faas.id for mapping metrics to generic_task

[dashpole]

In order to map to generic_task on cloud run, cloud functions, and GAE, we need to map from faas.name and faas.id to generic_task, similar to what we do for service.name and service.instance.id

Example in golang:

https://github.com/GoogleCloudPlatform/opentelemetry-operations-go/blob/ef9b15e0c12cee086ab8a6e7439e64258b029a3b/internal/resourcemapping/resourcemapping.go#L228-L235

Current implementation:

opentelemetry-operations-python/opentelemetry-resourcedetector-gcp/src/opentelemetry/resourcedetector/gcp_resource_detector/_mapping.py

Lines 168 to 173 in b0ca7de

	# fallback to generic_task
	if (
	ResourceAttributes.SERVICE_NAME in attrs
	and ResourceAttributes.SERVICE_INSTANCE_ID in attrs
	):
	mr = _create_monitored_resource(_constants.GENERIC_TASK, attrs)