refactor: rm math package dependencies

[milancermak]

Pull Request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Build-related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

The math package has a dependency on data_structures package only because the ed25519.cairo module uses 3 trivial functions from the SpanTraitExt trait. However, data_structures has a rather wild dependency tree by itself, so it pulls in encoding, numeric, bytes and searching 💀

What is the new behavior?

This PR removes the dependency of the math package on data_structures (and hence all its downstream deps) by adding (or rather, copy-pasting) two private functions (dedup and reverse) to the ed25519.cairo and replacing the third one (concat) by the use of append_span from Cairo core.

Does this introduce a breaking change?

• Yes
• No

Other information

There's no regression in performance of the ed25519.

Before this change:

$ scarb test -f ed255
running 7 tests
test alexandria_math::tests::ed25519_test::affine_point_op ... ok (gas usage est.: 411440)
test alexandria_math::tests::ed25519_test::verify_signature_invalid_length ... ok (gas usage est.: 5284792)
test alexandria_math::tests::ed25519_test::verify_signature_test_2 ... ok (gas usage est.: 390532238)
test alexandria_math::tests::ed25519_test::verify_signature_test_1 ... ok (gas usage est.: 382719878)
test alexandria_math::tests::ed25519_test::verify_signature_test_0 ... ok (gas usage est.: 389881208)
test alexandria_math::tests::ed25519_test::verify_signature_invalid ... ok (gas usage est.: 389229898)
test alexandria_math::tests::ed25519_test::verify_signature_test_3 ... ok (gas usage est.: 413750688)
test result: ok. 7 passed; 0 failed; 0 ignored; 143 filtered out;

After:

scarb test -f ed255
testing alexandria_math ...
running 7 tests
test alexandria_math::tests::ed25519_test::affine_point_op ... ok (gas usage est.: 411440)
test alexandria_math::tests::ed25519_test::verify_signature_invalid_length ... ok (gas usage est.: 5272652)
test alexandria_math::tests::ed25519_test::verify_signature_test_2 ... ok (gas usage est.: 390378618)
test alexandria_math::tests::ed25519_test::verify_signature_test_1 ... ok (gas usage est.: 382566258)
test alexandria_math::tests::ed25519_test::verify_signature_test_0 ... ok (gas usage est.: 389727588)
test alexandria_math::tests::ed25519_test::verify_signature_invalid ... ok (gas usage est.: 389076278)
test alexandria_math::tests::ed25519_test::verify_signature_test_3 ... ok (gas usage est.: 413597068)
test result: ok. 7 passed; 0 failed; 0 ignored; 143 filtered out;