Factor out and export config.LoadReceiver (#658)
Factor out and export config.LoadReceiver (#658)

* Factor out and export config.LoadReceiver

loadReceivers is being split into a singular version and exported called
LoadReceiver. This is needed to enable a new type of dynamic receiver that
itself can load and create receivers at runtime. To be able to load other
receivers at runtime it needs to be able to load their configs. The same
LoadReceiver code can be used for that as well as statically configured
receivers as they exist today.

* Revert change to go.sum
open-telemetry/opentelemetry-collector,open-telemetry/opentelemetry-collector-contrib,open-telemetry/opentelemetry-collector,open-telemetry/opentelemetry-collector-contrib,open-telemetry/opentelemetry-collector