Correct issues handling interest rate update events

[EdNoepel]

Moved logic for updating depositFeeRate into updatePool, eliminating the need for redundant getRateInfo calls. Centralized logic for handling rate resets and updates to a single method in base-pool.ts. Removed old fee rates from schema, since we cannot reliably provide them.

[EdNoepel]

Not convinced this is right yet. Experimentally, most of the fee rates have the same value for old and new. Investigating.

[EdNoepel]

Seems the problem is that the UpdateInterestRate event is coming after the TX has already mutated the state of the pool. For example, when a borrower draws debt, the DrawDebt event is emitted first, so handleDrawDebt calls updatePool, updating rates and fees. When the UpdateInterestRate is handled, the pool already has updated rates and fees, so the "old" values are reflecting the new state.

[EdNoepel]

Solution was to remove old fee rates from the event, as providing them would introduce more complexity than they were worth. Note that we can still provide the old lendRate, even though updatePool is likely to be called in the same TX before the interest rate update. This is because updatePool will recalculate lendRate using the old borrower rate, producing the same old number. Later on in the TX, borrow rate is updated and updatePool sets the new lendRate as appropriate.

[MikeHathaway]

LGTM

[tsifrer]

Looks good 👍 thank you