Ability to get delegator rewards and validator commissions

[blockrewards1]

Namada RPC doesn't have an endpoint to get a delegator's stake and rewards information. For example, cosmos-sdk has an easy to use API to get this information - /cosmos/distribution/v1beta1/delegators/{delegator_address}/rewards/{validator_address}

It would be great to have a similar endpoint in Namada undexer.

[mradkov]

This can be accomplished relatively straightforward by:

1. Modifying the pause/collect info on every epoch rather than how we currently do this (on every 2 epochs) using the undexer-pausable-node, before the node prunes the data. This is needed since the rewards information (https://github.com/anoma/namada/blob/08c16b74c0345542c5a89f5b4d60223ec47a10d9/crates/sdk/src/queries/vp/pos.rs#L106) is not epoched and the function above only displays data relative for the current epoch (and we want historical view).
2. Find the storage path in order to make an abci query and then store the result in the database once per epoch.
3. Extend dbQuery and dbRoutes with the necessary API endpoints to serve this info.