SQLAlchemy compliance: enable native ARRAY type support

[laughingman7743]

Context

Parent issue: #736

Athena supports native array<T> values, but the SQLAlchemy compliance requirement array_type is closed.
The dialect must expose ARRAY columns and values through a real SQLAlchemy array type before the requirement can be opened.

Scope

• Audit the current ARRAY type mapping, reflection, bind handling, and result handling.
• Map reflected Athena ARRAY columns to the appropriate PyAthena SQLAlchemy ARRAY type.
• Open the SQLAlchemy array_type requirement when the compliance tests pass.
• Preserve compatibility for existing AthenaArray users.

Acceptance criteria

• SQLAlchemy ARRAY compliance tests pass against Athena engine v3.
• Reflected ARRAY element types are preserved.
• Existing public ARRAY behavior remains backward compatible or the compatibility impact is documented.
• Compile-only regression tests cover type rendering where possible.
• just lint passes.
• Athena tests are limited to the affected nodes and run with -n 1.