Epic: Addresses & Keys Changes

[iAmMichaelConnor]

Following several rounds of discussions and decisions, here's a list of tasks relating to changes to addresses & keys.

### New address scheme
- [ ] Write an eng design doc for the new address scheme. Liaise w/ other teams (esp AVM).
- [ ] Implement the new address scheme across the stack
- [ ] https://github.com/AztecProtocol/aztec-packages/issues/8966

### Keys
- [ ] https://github.com/AztecProtocol/aztec-packages/issues/9162
- [x] Remove code relating to key rotation
- [x] Remove the key registry
- [ ] https://github.com/AztecProtocol/aztec-packages/issues/8969
- [ ] https://github.com/AztecProtocol/aztec-packages/issues/8970
- [ ] https://github.com/AztecProtocol/aztec-packages/issues/8999
- [ ] P1: Internal Incoming Viewing Keys

### p1: Plume
- [ ] Liaise w/ Crypto Research to ensure security of approach for Plume w/ Grumpkin & Posiedon2 [Mike to do]
- [ ] Run the latest flamegraph of the reset private kernel circuit, to determine the constraint counts for one key validation request. Compare it against 3300 for plume.
- [ ] Implement an example flow of using plume nullifiers.
- [ ] Fun: Explore how to add Grumpkin ops as an 'app' on Ledger hardware wallets.
- [ ] Example Escrow contract