The batching log processor will generate records from 4 different
locations (polling, OnEmit, ForceFlush, Shutdown). In order to ensure an
Exporter is called serially, as is required by the interface, this
function will be used in the processor to centralize the interaction
with its Exporter.

Part of open-telemetry#5063.

See open-telemetry#5093 for the implementation use.