Improve indexing

[Wizdave97]

Let's link the AssetTeleported and TokenGatewayAssetTeleported events to the request entity via the commitment on those events, so both models can be fetched at once.

We'll have to modify the entity names

Let's create an entity that indexes each relayer's reward for each transaction. Right now, we only index cumulative rewards; we want to be able to fetch a list of transactions where a relayer was rewarded.

Same goes for collator rewards.