Backend SQL SPO auto-voting options

### What?

The predefined voting options for SPOs
are based upon the delegation of the SPO's rewards account

> Note Any wallet serving as the Registered Reward Wallet for a Stake Pool can be delegated to one of these Pre-defined Voting Options and doing so will serve as the default voting option selected by the SPO for all Governance Action votes, excepting Hard Fork Governance Actions. Due to the need for robust consensus around Hard Fork initiations, these votes must be met as a percentage of the stake held by all stake pools.

### Changes

The current equation for Outcomes uses the Pool Owners for definition of predefined
- https://github.com/IntersectMBO/govtool-outcomes-pillar/blob/main/backend/src/queries/networkMetrics.ts#L119C5-L119C45

I believe this should be changed to reference the rewards account
something like

```sql
pool_update.reward_addr_id
```

so using the pool_update table to get the most recent reward address for the pool

Start in backend/src/queries/networkMetrics.ts around line 119 and inspect how the Outcomes equation currently identifies pool owners. Trace the pool_update table and its reward_addr_id values, including how to select the most recent reward address for a pool. Done means predefined SPO voting options are based on the rewards account rather than the pool owner.

Written by the indexing model from the issue text.