Describe the feature

we often do:

to obtain a stream of new receipts, which flashblocks we also want a way to provide a stream of receipts

that combines the canonical state stream with flashblocks:

we can do this by writing a custom flashblocks aware stream primitive that uses both streams as input and yields Receipts, for new blocks
this needs to tracks latest yielded block, so that we avoid yielding duplicate receipts

Additional context

assigning @mablr