Finish `HistoryNetwork` buildout

[acolytec3]

This is a meta issue to track what's left for Ultralight to be production ready for History Network

• - Implement deneb types per here, HistoryNetwork updates #776
• - Ephemeral Headers types - Add types and store support for Ephemeral Headers #778
• - Send and handle FINDCONTENT requests Add types and store support for Ephemeral Headers #778 Return ephemeral headers in FOUNDCONTENT #744, Implement support for ephemeral headers #733
• - Purge old ephemeral headers once headers with proofs are received
• - Neighborhood gossip OFFERed ephemeral headers
• - Add ephemeral headers support to eth_getBlockBy* RPC endpoints
  • - Search for ephemeral headers if not found in standard History Network contentIds (HeaderWithProof, HeaderByNumber)
  • - Search for latest in ephemeral headers (based on lightclient.getHead)
• - Validate OFFERed ephemeral headers against latest head from light client update Implement handleOffer for ephemeral headers #784