Correct input comparison for input-subset RBF bump creation

This resolves a regression introduced in "Implement bumping engine in
ChannelMonitor::block_connected" in which not all inputs are checked.
Several opportunities to clarify and clean up comments are also taken.

Fix test_bump_penalty_txn_on_revoked_htlcs as now remote claim txn
build the same way than us are going to be register as cleaning
pending_claim_request after ANTI_REORG_DELAY. It means during this
delay we are going to generate invalid bumped claiming txn on
already claimed outpoints. Previously these txn weren't issued
because all their outpoints would have been removed.

Fix full_stack_target by adding more input for FuzzEstimator

Author: TheBlueMatt