otel: retries must be tracked per-call and not per-attempt #8700
Description
The number of retries is currently tracked inside the attemptInfo here:
grpc-go/stats/opentelemetry/opentelemetry.go
Line 244 in e816736
And a new attemptInfo is created for every attempt here:
grpc-go/stats/opentelemetry/client_metrics.go
Line 155 in e816736
We need to track this in the callInfo instead, so that we can increment the number of retries for a call:
grpc-go/stats/opentelemetry/opentelemetry.go
Line 174 in e816736
We had a PR that attempted to do this earlier: #8342, but it introduced a flaky test and therefore had to be rolled back.