Fixes#6211.
In Go-land packages with the same name, e.g., internal, do not clash
with each other when they're in different parts of the project. However
with protobufs definitions will clash if they share the same package
name.
This commit renames the influxql protobuf package to `influxql` to
avoid a clash with a message definition in another protobuf package
called internal. Go package aliases allow us to continue to refer to the
internal package as `internal` rather than `influxql`.
This commit adds an `IteratorStats` that holds aggregate
iterator processing information. A method is also added to
`Iterator` to return the stats:
Stats() influxql.IteratorStats
The remote iterators will also emit their stats in the point
stream upon first connection, on a given interval, and then
finally once the last point has been sent.
Edd Robinson
Ben Johnson