[stateless_validation] Chunk endorsements spam protection

[staffik]

nearcore/chain/client/src/chunk_validation.rs

Line 575 in 55f5586

// TODO(stateless_validation): It's possible for a malicious validator to send endorsements

We need to figure out if there's a possible security concern if someone spams the network with a lot of chunk endorsements and if we can come up with a heuristic to prevent this from happening.
Currently we are sending chunk endorsements to the next 5 block producers, but when a block producer receives an endorsement they still need to save it till it's potentially used.
process_chunk_endorsement is the first function that gets called from the network stack on receiving a chunk endorsement.

[staffik]

#10522 (comment)