To enable: --experiment.persist.receipts=10_000
Details:

• Persistence: happening only on ChainTip and "lazy". Lazy - means it persist receipts of new executed blocks (amount will grow with time - up to a --experiment.persist.receipts=10_000 limit) and prune later
• Stored in ChaindataDB - means no loss after at Erigon restart
• Storing and canonical and non-canonical receipts (no deletes on unwind)
• RPC and P2P requests are covered
• Values: 1_000 good starting point. 10_000 receitps it's ~1Gb (not much IO increase). Please test on your setup if you want to go over 100_000

Idea: Decided to not subscribe RPCD to new Erigon's receipts. Persistence in db means:

• new receipts available for readers immediately (on gap in async event delivery)
• can afford to store "denormalized, and non-optimized" version of receipt - not like in E2 - because we do store not much receipts
• receipts LRU doesn't need to cache receipts if we found it in DB. because DB it's already kind-of cache (small, mmaped, hot file). It means - receipts LRU will cover only old receipts - which has different access pattern from recent.