Improve FieldElement struct construction

[tcoratger]

Description

This pull request refactors the FieldElement structure to remove the unnecessary inner field, enhancing efficiency and minimizing struct size. Additionally, it implements the std::ops::Deref and std::ops::DerefMut traits to facilitate standard struct manipulations.

Changes

• Removed the inner field from the FieldElement structure.
• Implemented std::ops::Deref and std::ops::DerefMut traits for improved struct operations.

Impact

• Improved efficiency by eliminating redundant struct fields.
• Reduced struct size for better memory optimization.
• Simplified struct manipulation with the addition of trait implementations.

[xJonathanLEI]

TBH I don't think the inner part makes any difference. I could be wrong but I think a single field struct should be exactly equivalent to a newtype struct in terms of performance. So changing that for better performance doesn't feel justified.

[tcoratger]

TBH I don't think the inner part makes any difference. I could be wrong but I think a single field struct should be exactly equivalent to a newtype struct in terms of performance. So changing that for better performance doesn't feel justified.

This one doesn't seem really relevant since we have this one in the pipeline: #562 which will delete all of this.

[xJonathanLEI]

Yeah that's true.

[xJonathanLEI]

starknet-ff was removed as part of #562. Closing this now as it's no longer relevant.