Migrate towerAlgebraMap recursion to Fin.dfoldl

[dhsorens]

Context

CompPoly/Fields/Binary/Tower/Basic.lean includes a TODO near towerAlgebraMap:

migrate to Fin.dfoldl

Proposed work

• Refactor towerAlgebraMap to use Fin.dfoldl instead of the current recursive style.
• Keep theorem statements/API unchanged.

Acceptance criteria

• Existing callers of towerAlgebraMap require no API changes.
• proofs and/or tests to show correctness

[erdkocak]

I am working on this, I am hoping to open up a pr tomorrow.