Implement fungible Substrate transfer

[MakMuftic]

Following the proposed v3 SDK restructure, implement/restructure the necessary functions for creating deposit Substrate transactions for fungible assets.

Implementation details

Check packages/substrate/src/fungible.ts for the interface definitions.

Testing details

• Restructure and update existing unit tests (expand if required)
• Validate manually that refactored substrate-to-evm-fungible-transfer-example is passing on testnet

QA Details

• New exposed interfaces and functions should allow the same functionalities as the v2 SDK implementation, such as the creation of fungible Substrate transfers and the estimation of fees.

Acceptance Criteria

• [ ] Implementing fungible Substrate transfers following v3 guidlines
• [ ] Restructure and update existing unit tests
• [ ] Update substrate-to-evm-fungible-transfer-example example to use v3 implementation
• [ ] Validate substrate-to-evm-fungible-transfer-example example manually on testnet