Add monitoring for USDG

[spalen0]

Check what we should monitor: https://github.com/yearn/risk-score/blob/master/reports/report/paxos-usdg.md#monitoring

Focus only following parts of monitoring:

1. NAV/Share: Track Continuous Price Oracle and Chainlink feed — should increase monotonically. Alert on any decrease (would indicate fund losses). Also, alert ifthe difference is bigger than 0.5%
2. RedemptionIdle - USDC balance (redemption capacity), large redemptions. trigger when below 0.5m
3. ustb price check as other stables.
4. Large Supply Changes: Alert on >+10% of total supply in 24h.
5. Oracle stale check:

• Read checkpoints(roundId).effectiveAt where roundId = latestRoundData().roundId
• Staleness = block.timestamp - effectiveAt
• Alert if > 4 days (345600s) — revert happens at 5 days (432000s)

points 1 and 2 should be in same script and run hourly. point 3 can be part of stables.