Prior to this commit, the `GraphQlObservationInstrumentation` would
instrument the following operations:
* GraphQL requests
* GraphQL data fetching operations
In the case of batch loading operations, the instrumentation would
consider each load call as a separate data fetching operation. This
would significantly clutter recorded traces and would make it look like
"N+1 problems" would still be present.
This commit adds a new "graphql.dataloader" observation for such
operations and avoids recording data fetching observations when
`SelfDescribingDataFetcher` declare that they call batch loading
operations.
Closes gh-1034
594c9dfc4f