Snapshot Forwarders

[Umaaz]

Tempo supports forwarders that allow received traces to be forwarded to other services.

Deep has this functionality but it has not been updated to use snapshots.

• distributor: needs update to create snapshot forwarders
• config: forward config refers to otl, this should change to snapshots
• example/test: should create a simple receiver that can be configured as a forwarder to allow testing/example
• Change metric forwarder to be the same/similar to the dynamic types?

[Umaaz]

The forwarders use otl export service to export spans to external services. To replicate this we should create a public export service (or use the current grpc send service). Then use this to support exporting the data.