Add a base pool class to consolidate the propose_power and related methods

[llucax]

What's needed?

We have 3 different pools now, all using the same interface for managing power, but they don't share a common ancestor, so these methods could eventually inadvertently diverge, which is not what we want.

Proposed solution

Add an abstract base class to define the common interface of all pools so we can ensure they keep the same interface.

It should have at least the propose_power and power and power_status methods.

The name might be tricky, maybe PowerManagingComponentPool?

Additional context

Coming from:

• Add a PVPool implementation #914 (comment)