In #23227 we added cpdef declarations to address most of cython/cython#1732. A few were not completely straightforward and will be dealt with in follow-up tickets:

1. sage/algebras/quatalg/quaternion_algebra_element.pxd: Add abstract _add_ and _mul_ methods to RingElement #24607

2. sage/modular/pollack_stevens: Fix cpdef declaration issues in modular and number fields #23603

3. sage/modules: Add abstract _add_ and _mul_ methods to RingElement #24607

4. sage/numerical/backends: MIP backends: Unify add_col, add_variable; and clarify defaulting behavior of binary, continuous, integer #20324

5. sage/rings/finite_rings: Fix Cython warnings in finite_rings #24116 and Add abstract _add_ and _mul_ methods to RingElement #24607

6. sage/rings/number_field: Fix cpdef declaration issues in modular and number fields #23603

7. sage/rings/padics: Fix Cython vtable warnings in padic_generic_element.pyx #27417, Cython vtable warnings in padics #24609

8. sage/rings/polynomial/laurent_polynomial.pxd: Add some abstract methods to Laurent polynomials base class #23606

9. sage/rings/power_series_*: Add abstract _add_ and _mul_ methods to RingElement #24607 and Remove deprecated PowerSeries._floordiv_ #24608

CC: @jdemeyer

Component: cython

Issue created by migration from https://trac.sagemath.org/ticket/23600