Refactor IntegerMulAction in preparation for #24247:

1. Add an abstract base class IntegerAction which will also be used to implement IntegerPowAction in Implement __pow__ in the coercion model #24247.

2. Add a new helper function parent_is_integers to check if some type/parent represents the integers.

3. Instead of the hacks in discover_action and verify_action involving an explicit IntegerMulAction check, return an IntegerMulAction for anything satisfying parent_is_integers().

Component: coercion

Author: Jeroen Demeyer

Branch/Commit: a359862

Reviewer: Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/24467