Post-clustermempool package RBF: per-chunk processing

[glozow]

@sipa

Verification: verify all transactions in PKG under standard/policy rules (including script verification). If this fails, continue with the next chunk. Otherwise, the chunk is a valid and desirable addition/replacement to the mempool.

Quick clarification: is this step happening for all transactions in CNK or in PKG? I understood this to be within the chunk loop?