The upcoming launch of Nabla requires that some assets have full ERC20 functionality, particularly to allow smart contracts to transfer tokens on behalf of a user.

This feature is managed in the `TokenAllowance` pallet and the pallet will only equip allow listed assets with this feature.

This is a proposal to allow list the following assets:
* USDC.s,
* BRL.s,
* EURC.s,
* TZS.s,
* AUDD.s,
* NGNC.s,
* USDT from AssetHub,
* BRZ from AssetHub

Schedule a majority-carries referendum to be tabled next once it is legal to schedule
an external referendum.

The dispatch of this call must be `ExternalMajorityOrigin`.

- `proposal_hash`: The preimage hash of the proposal.

Unlike `external_propose`, blacklisting has no effect on this and it may replace a
pre-scheduled `external_propose` call.

Weight: `O(1)`

Added allowed currencies that possible to use chain extension

# Arguments
* `currencies` - list of currency id allowed to use in chain extension

- **Problem Statement:** Implementing full ERC20 functionality for assets like USDC.s, BRL.s, EURC.s, TZS.s, AUDD.s, NGNC.s, USDT, and BRZ for the upcoming Nabla launch.
- **Significance:** Ensuring smart contracts can transfer tokens on behalf of users, enhancing functionality for the Nabla launch.
- **Proposed Solution:** Allow listing the specified assets in the `TokenAllowance` pallet to enable ERC20 functionality.
- **Expected Outcomes:** Enhanced functionality for smart contracts, facilitating seamless token transfers for users during the Nabla launch.

#27 Allowlist assets for full ERC20 support