fix: Transfer excess back and reset allowance

[miguelmtzinf]

This PR applies two significant changes to the debt swap action:

• Resets the allowance from the adapter contract to the Augustus contract after Paraswap execution. This ensures no pending allowance is left.
• Transfers excess of assets after the swap to the user. This ensures that in case the buy is not completely "exact out", the excess will be transferred to the user rather than remaining within the contract.

This introduces similar changes to aave-dao/aave-v3-origin#49

[miguelmtzinf]

Commit c53ea9f implements significant modifications due to the allowances configuration from the adapter to the Aave pool. We can opt to discard these changes to keep modifications minimal and proceed under the assumption that interactions with Aave are secure.