Managed pools

Can we bring them back with a more limited scope in V3?

We need:
- Weight change functionality (permissioned, smoothed over time)
  - Check out QuantAMM first
- Replacing tokens?
  - Migration system. Users will not hold BPT directly, but a wrapped derivative.
  - 1:1 redeemable with BPT in principle. We can use this for AUM fees later on.
- Dynamic fees?