Only check allowance of liquidity sources that are actually used

[MartinquaXD]

Description

Currently a lot of CPU time (~3.5%) is spent on fetching allowances for the liquidity sources we index. This is problematic for 2 reasons:

• most liquidity sources are not used so fetching the settlement contract's allowance is wasted time
• the driver seems to not use the fetched allowance and fetches them again when encoding the tx (see 1, 2, 3, 4)

Changes

deleted solver::interactions::allowances and it's usages

How to test

e2e tests still work

[gemini-code-assist]

Code Review

This pull request removes the pre-fetching of allowances for liquidity sources to improve performance, based on the assumption that these allowances are fetched again later in the transaction encoding process. The implementation correctly removes the solver::interactions::allowances module and its usages across various liquidity source implementations. However, a critical issue has been identified: tests in multiple files have been commented out instead of being updated or removed. This significantly reduces test coverage and confidence in the correctness of the changes. The tests must be restored and adapted to the new logic.

[gemini-code-assist]

Code Review

The changes remove allowance fetching logic from the solver, deferring it to the driver. This has been applied consistently across all liquidity sources. No critical issues found.

[jmg-duarte]

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