The ProtobufDecoder will decode message delimited protobuf messages from prom_model.proto types
They are delimited by size, eg a format is such:
[]byte{size, data, size, data, size, data}, etc
convert_to_remote_write is an expensive method due to the time it takes to submit to mimir.
other operations here are optimized for async, within reason. The post process uses a single
connection to mimir and thus incurs the seriliaztion delay for each metric family sent. Possible
future optimizations would be to use multiple tcp connections to mimir, within reason. Nevertheless
we await on each post of each metric family so it shouldn’t block any other async work in a
significant way.