This commit adds the required infrastructure for instrumenting the
GraphQL engine and datafetchers in order to collect metrics.
With this infrastructure, we can collect metrics such as:
* "graphql.request", a timer for GraphQL query
* "graphql.datafetcher", a timer for GraphQL datafetcher calls
* "graphql.request.datafetch.count", a distribution summary of
datafetcher count per query
* "graphql.error", an error counter
See gh-29140
a7839bc9b9