improvement: add cancel txn to offer

[denverbaumgartner]

currently, on both RubiconV2 and RubiconV2_Optimism we are not tracking the transaction that caused the offer to be cancelled. for now, it probably makes the most since just to record the transaction regardless of whether it was a take, cancel, or min order sell cancel on the offer. this removes some level of insight into the cause of the cancel, but solves our immediate needs today. this will be an update to the Offer entity, and will occur any place we are updating the removed_timestamp.