Replace token implementations with standard.

[LHerskind]

Replace the token implementations throughout the example contracts with the standard token.

### Tasks
- [ ] https://github.com/AztecProtocol/aztec-packages/issues/2273
- [x] Replace `non_native_token_contract` usage.
- [ ] https://github.com/AztecProtocol/aztec-packages/issues/2279
- [x] Replace `public_token_contract` usage. *
- [x] Replace `private_token_airdrop_contract` usage. Should be replaced with separate contract and not make an airdrop and token be the same contract. *
- [ ] https://github.com/AztecProtocol/aztec-packages/issues/2938
- [ ] https://github.com/AztecProtocol/aztec-packages/issues/2291

• might be deleted along with its tests if completely covered by standard.

### Dependencies
- [ ] https://github.com/AztecProtocol/aztec-packages/issues/1743
- [ ] https://github.com/AztecProtocol/aztec-packages/issues/2170